[PATCH 0/2] capability conversion fixes

STALE2086d

9 messages, 3 authors, 2021-01-26 · open the first message on its own page

[PATCH 0/2] capability conversion fixes

From: Miklos Szeredi <hidden>
Date: 2021-01-19 18:27:51

It turns out overlayfs is actually okay wrt. mutliple conversions, because
it uses the right context for lower operations.  I.e. before calling
vfs_{set,get}xattr() on underlying fs, it overrides creds with that of the
mounter, so the current user ns will now match that of
overlay_sb->s_user_ns, meaning that the caps will be converted to just the
right format for the next layer

OTOH ecryptfs, which is the only other one affected by commit 7c03e2cda4a5
("vfs: move cap_convert_nscap() call into vfs_setxattr()") needs to be
fixed up, since it doesn't do the cap override thing that overlayfs does.

I don't have an ecryptfs setup, so untested, but it's a fairly trivial
change.

My other observation was that cap_inode_getsecurity() messes up conversion
of caps in more than one case.  This is independent of the overlayfs user
ns enablement but affects it as well.

Maybe we can revisit the infrastructure improvements we discussed, but I
think these fixes are more appropriate for the current cycle.

Thanks,
Miklos

Miklos Szeredi (2):
  ecryptfs: fix uid translation for setxattr on security.capability
  security.capability: fix conversions on getxattr

 fs/ecryptfs/inode.c  | 10 +++++--
 security/commoncap.c | 67 ++++++++++++++++++++++++++++----------------
 2 files changed, 50 insertions(+), 27 deletions(-)

-- 
2.26.2

[PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability

From: Miklos Szeredi <hidden>
Date: 2021-01-19 18:27:51

Prior to commit 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into
vfs_setxattr()") the translation of nscap->rootid did not take stacked
filesystems (overlayfs and ecryptfs) into account.

That patch fixed the overlay case, but made the ecryptfs case worse.

Restore old the behavior for ecryptfs that existed before the overlayfs
fix.  This does not fix ecryptfs's handling of complex user namespace
setups, but it does make sure existing setups don't regress.

Reported-by: Eric W. Biederman <redacted>
Cc: Tyler Hicks <code@tyhicks.com>
Fixes: 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into vfs_setxattr()")
Signed-off-by: Miklos Szeredi <redacted>
---
 fs/ecryptfs/inode.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index e23752d9a79f..58d0f7187997 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c

@@ -1016,15 +1016,19 @@ ecryptfs_setxattr(struct dentry *dentry, struct inode *inode,
 {
 	int rc;
 	struct dentry *lower_dentry;
+	struct inode *lower_inode;
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
-	if (!(d_inode(lower_dentry)->i_opflags & IOP_XATTR)) {
+	lower_inode = d_inode(lower_dentry);
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		rc = -EOPNOTSUPP;
 		goto out;
 	}
-	rc = vfs_setxattr(lower_dentry, name, value, size, flags);
+	inode_lock(lower_inode);
+	rc = __vfs_setxattr_locked(lower_dentry, name, value, size, flags, NULL);
+	inode_unlock(lower_inode);
 	if (!rc && inode)
-		fsstack_copy_attr_all(inode, d_inode(lower_dentry));
+		fsstack_copy_attr_all(inode, lower_inode);
 out:
 	return rc;
 }

-- 
2.26.2

[PATCH 2/2] security.capability: fix conversions on getxattr

From: Miklos Szeredi <hidden>
Date: 2021-01-19 18:27:51

If a capability is stored on disk in v2 format cap_inode_getsecurity() will
currently return in v2 format unconditionally.

This is wrong: v2 cap should be equivalent to a v3 cap with zero rootid,
and so the same conversions performed on it.

If the rootid cannot be mapped v3 is returned unconverted.  Fix this so
that both v2 and v3 return -EOVERFLOW if the rootid (or the owner of the fs
user namespace in case of v2) cannot be mapped in the current user
namespace.

Signed-off-by: Miklos Szeredi <redacted>
---
 security/commoncap.c | 67 ++++++++++++++++++++++++++++----------------
 1 file changed, 43 insertions(+), 24 deletions(-)

diff --git a/security/commoncap.c b/security/commoncap.c
index bacc1111d871..c9d99f8f4c82 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c

@@ -371,10 +371,11 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 {
 	int size, ret;
 	kuid_t kroot;
+	__le32 nsmagic, magic;
 	uid_t root, mappedroot;
 	char *tmpbuf = NULL;
 	struct vfs_cap_data *cap;
-	struct vfs_ns_cap_data *nscap;
+	struct vfs_ns_cap_data *nscap = NULL;
 	struct dentry *dentry;
 	struct user_namespace *fs_ns;

@@ -396,46 +397,61 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 	fs_ns = inode->i_sb->s_user_ns;
 	cap = (struct vfs_cap_data *) tmpbuf;
 	if (is_v2header((size_t) ret, cap)) {
-		/* If this is sizeof(vfs_cap_data) then we're ok with the
-		 * on-disk value, so return that.  */
-		if (alloc)
-			*buffer = tmpbuf;
-		else
-			kfree(tmpbuf);
-		return ret;
-	} else if (!is_v3header((size_t) ret, cap)) {
-		kfree(tmpbuf);
-		return -EINVAL;
+		root = 0;
+	} else if (is_v3header((size_t) ret, cap)) {
+		nscap = (struct vfs_ns_cap_data *) tmpbuf;
+		root = le32_to_cpu(nscap->rootid);
+	} else {
+		size = -EINVAL;
+		goto out_free;
 	}
 
-	nscap = (struct vfs_ns_cap_data *) tmpbuf;
-	root = le32_to_cpu(nscap->rootid);
 	kroot = make_kuid(fs_ns, root);
 
 	/* If the root kuid maps to a valid uid in current ns, then return
 	 * this as a nscap. */
 	mappedroot = from_kuid(current_user_ns(), kroot);
 	if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
+		size = sizeof(struct vfs_ns_cap_data);
 		if (alloc) {
-			*buffer = tmpbuf;
+			if (!nscap) {
+				/* v2 -> v3 conversion */
+				nscap = kzalloc(size, GFP_ATOMIC);
+				if (!nscap) {
+					size = -ENOMEM;
+					goto out_free;
+				}
+				nsmagic = VFS_CAP_REVISION_3;
+				magic = le32_to_cpu(cap->magic_etc);
+				if (magic & VFS_CAP_FLAGS_EFFECTIVE)
+					nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
+				memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
+				nscap->magic_etc = cpu_to_le32(nsmagic);
+			} else {
+				/* use allocated v3 buffer */
+				tmpbuf = NULL;
+			}
 			nscap->rootid = cpu_to_le32(mappedroot);
-		} else
-			kfree(tmpbuf);
-		return size;
+			*buffer = nscap;
+		}
+		goto out_free;
 	}
 
 	if (!rootid_owns_currentns(kroot)) {
-		kfree(tmpbuf);
-		return -EOPNOTSUPP;
+		size = -EOVERFLOW;
+		goto out_free;
 	}
 
 	/* This comes from a parent namespace.  Return as a v2 capability */
 	size = sizeof(struct vfs_cap_data);
 	if (alloc) {
-		*buffer = kmalloc(size, GFP_ATOMIC);
-		if (*buffer) {
-			struct vfs_cap_data *cap = *buffer;
-			__le32 nsmagic, magic;
+		if (nscap) {
+			/* v3 -> v2 conversion */
+			cap = kzalloc(size, GFP_ATOMIC);
+			if (!cap) {
+				size = -ENOMEM;
+				goto out_free;
+			}
 			magic = VFS_CAP_REVISION_2;
 			nsmagic = le32_to_cpu(nscap->magic_etc);
 			if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)

@@ -443,9 +459,12 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 			cap->magic_etc = cpu_to_le32(magic);
 		} else {
-			size = -ENOMEM;
+			/* use unconverted v2 */
+			tmpbuf = NULL;
 		}
+		*buffer = cap;
 	}
+out_free:
 	kfree(tmpbuf);
 	return size;
 }

-- 
2.26.2

Re: [PATCH 2/2] security.capability: fix conversions on getxattr

From: kernel test robot <hidden>
Date: 2021-01-20 19:42:05

Hi Miklos,

I love your patch! Perhaps something to improve:

[auto build test WARNING on security/next-testing]
[also build test WARNING on linux/master linus/master v5.11-rc4 next-20210120]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Miklos-Szeredi/capability-conversion-fixes/20210120-152933
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git next-testing
config: xtensa-randconfig-s032-20210120 (attached as .config)
compiler: xtensa-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-208-g46a52ca4-dirty
        # https://github.com/0day-ci/linux/commit/bcf70adf8bcc3e52cb1b262ae2e1d9154da75097
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Miklos-Szeredi/capability-conversion-fixes/20210120-152933
        git checkout bcf70adf8bcc3e52cb1b262ae2e1d9154da75097
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=xtensa 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>


"sparse warnings: (new ones prefixed by >>)"
   security/commoncap.c:424:41: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] nsmagic @@     got int @@
   security/commoncap.c:424:41: sparse:     expected restricted __le32 [usertype] nsmagic
   security/commoncap.c:424:41: sparse:     got int

quoted

security/commoncap.c:425:39: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] magic @@     got unsigned int @@

   security/commoncap.c:425:39: sparse:     expected restricted __le32 [usertype] magic
   security/commoncap.c:425:39: sparse:     got unsigned int
   security/commoncap.c:426:37: sparse: sparse: restricted __le32 degrades to integer
   security/commoncap.c:427:49: sparse: sparse: invalid assignment: |=
   security/commoncap.c:427:49: sparse:    left side has type restricted __le32
   security/commoncap.c:427:49: sparse:    right side has type int
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32

quoted

security/commoncap.c:429:52: sparse: sparse: incorrect type in argument 1 (different base types) @@     expected unsigned int [usertype] val @@     got restricted __le32 [usertype] nsmagic @@

   security/commoncap.c:429:52: sparse:     expected unsigned int [usertype] val
   security/commoncap.c:429:52: sparse:     got restricted __le32 [usertype] nsmagic
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32
   security/commoncap.c:455:31: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] magic @@     got int @@
   security/commoncap.c:455:31: sparse:     expected restricted __le32 [usertype] magic
   security/commoncap.c:455:31: sparse:     got int
   security/commoncap.c:456:33: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] nsmagic @@     got unsigned int @@
   security/commoncap.c:456:33: sparse:     expected restricted __le32 [usertype] nsmagic
   security/commoncap.c:456:33: sparse:     got unsigned int
   security/commoncap.c:457:29: sparse: sparse: restricted __le32 degrades to integer
   security/commoncap.c:458:39: sparse: sparse: invalid assignment: |=
   security/commoncap.c:458:39: sparse:    left side has type restricted __le32
   security/commoncap.c:458:39: sparse:    right side has type int
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:460:42: sparse: sparse: incorrect type in argument 1 (different base types) @@     expected unsigned int [usertype] val @@     got restricted __le32 [usertype] magic @@
   security/commoncap.c:460:42: sparse:     expected unsigned int [usertype] val
   security/commoncap.c:460:42: sparse:     got restricted __le32 [usertype] magic
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:1281:41: sparse: sparse: dubious: !x | y

vim +425 security/commoncap.c

   357	
   358	/*
   359	 * getsecurity: We are called for security.* before any attempt to read the
   360	 * xattr from the inode itself.
   361	 *
   362	 * This gives us a chance to read the on-disk value and convert it.  If we
   363	 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
   364	 *
   365	 * Note we are not called by vfs_getxattr_alloc(), but that is only called
   366	 * by the integrity subsystem, which really wants the unconverted values -
   367	 * so that's good.
   368	 */
   369	int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
   370				  bool alloc)
   371	{
   372		int size, ret;
   373		kuid_t kroot;
   374		__le32 nsmagic, magic;
   375		uid_t root, mappedroot;
   376		char *tmpbuf = NULL;
   377		struct vfs_cap_data *cap;
   378		struct vfs_ns_cap_data *nscap = NULL;
   379		struct dentry *dentry;
   380		struct user_namespace *fs_ns;
   381	
   382		if (strcmp(name, "capability") != 0)
   383			return -EOPNOTSUPP;
   384	
   385		dentry = d_find_any_alias(inode);
   386		if (!dentry)
   387			return -EINVAL;
   388	
   389		size = sizeof(struct vfs_ns_cap_data);
   390		ret = (int) vfs_getxattr_alloc(dentry, XATTR_NAME_CAPS,
   391					 &tmpbuf, size, GFP_NOFS);
   392		dput(dentry);
   393	
   394		if (ret < 0)
   395			return ret;
   396	
   397		fs_ns = inode->i_sb->s_user_ns;
   398		cap = (struct vfs_cap_data *) tmpbuf;
   399		if (is_v2header((size_t) ret, cap)) {
   400			root = 0;
   401		} else if (is_v3header((size_t) ret, cap)) {
   402			nscap = (struct vfs_ns_cap_data *) tmpbuf;
   403			root = le32_to_cpu(nscap->rootid);
   404		} else {
   405			size = -EINVAL;
   406			goto out_free;
   407		}
   408	
   409		kroot = make_kuid(fs_ns, root);
   410	
   411		/* If the root kuid maps to a valid uid in current ns, then return
   412		 * this as a nscap. */
   413		mappedroot = from_kuid(current_user_ns(), kroot);
   414		if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
   415			size = sizeof(struct vfs_ns_cap_data);
   416			if (alloc) {
   417				if (!nscap) {
   418					/* v2 -> v3 conversion */
   419					nscap = kzalloc(size, GFP_ATOMIC);
   420					if (!nscap) {
   421						size = -ENOMEM;
   422						goto out_free;
   423					}
   424					nsmagic = VFS_CAP_REVISION_3;
 > 425					magic = le32_to_cpu(cap->magic_etc);
   426					if (magic & VFS_CAP_FLAGS_EFFECTIVE)
   427						nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
   428					memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 > 429					nscap->magic_etc = cpu_to_le32(nsmagic);
   430				} else {
   431					/* use allocated v3 buffer */
   432					tmpbuf = NULL;
   433				}
   434				nscap->rootid = cpu_to_le32(mappedroot);
   435				*buffer = nscap;
   436			}
   437			goto out_free;
   438		}
   439	
   440		if (!rootid_owns_currentns(kroot)) {
   441			size = -EOVERFLOW;
   442			goto out_free;
   443		}
   444	
   445		/* This comes from a parent namespace.  Return as a v2 capability */
   446		size = sizeof(struct vfs_cap_data);
   447		if (alloc) {
   448			if (nscap) {
   449				/* v3 -> v2 conversion */
   450				cap = kzalloc(size, GFP_ATOMIC);
   451				if (!cap) {
   452					size = -ENOMEM;
   453					goto out_free;
   454				}
   455				magic = VFS_CAP_REVISION_2;
   456				nsmagic = le32_to_cpu(nscap->magic_etc);
   457				if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
   458					magic |= VFS_CAP_FLAGS_EFFECTIVE;
   459				memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
   460				cap->magic_etc = cpu_to_le32(magic);
   461			} else {
   462				/* use unconverted v2 */
   463				tmpbuf = NULL;
   464			}
   465			*buffer = cap;
   466		}
   467	out_free:
   468		kfree(tmpbuf);
   469		return size;
   470	}
   471	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH 2/2] security.capability: fix conversions on getxattr

From: kernel test robot <hidden>
Date: 2021-01-20 22:12:30

Hi Miklos,

I love your patch! Perhaps something to improve:

[auto build test WARNING on security/next-testing]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Miklos-Szeredi/capability-conversion-fixes/20210120-152933
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git next-testing
config: x86_64-randconfig-s022-20210120 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-208-g46a52ca4-dirty
        # https://github.com/0day-ci/linux/commit/bcf70adf8bcc3e52cb1b262ae2e1d9154da75097
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Miklos-Szeredi/capability-conversion-fixes/20210120-152933
        git checkout bcf70adf8bcc3e52cb1b262ae2e1d9154da75097
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>


"sparse warnings: (new ones prefixed by >>)"

quoted

security/commoncap.c:424:41: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] nsmagic @@     got int @@

   security/commoncap.c:424:41: sparse:     expected restricted __le32 [usertype] nsmagic
   security/commoncap.c:424:41: sparse:     got int

quoted

security/commoncap.c:425:39: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] magic @@     got unsigned int [usertype] @@

   security/commoncap.c:425:39: sparse:     expected restricted __le32 [usertype] magic
   security/commoncap.c:425:39: sparse:     got unsigned int [usertype]
   security/commoncap.c:426:37: sparse: sparse: restricted __le32 degrades to integer
   security/commoncap.c:427:49: sparse: sparse: invalid assignment: |=
   security/commoncap.c:427:49: sparse:    left side has type restricted __le32
   security/commoncap.c:427:49: sparse:    right side has type int
   security/commoncap.c:429:52: sparse: sparse: cast from restricted __le32
   security/commoncap.c:455:31: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] magic @@     got int @@
   security/commoncap.c:455:31: sparse:     expected restricted __le32 [usertype] magic
   security/commoncap.c:455:31: sparse:     got int
   security/commoncap.c:456:33: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le32 [usertype] nsmagic @@     got unsigned int [usertype] @@
   security/commoncap.c:456:33: sparse:     expected restricted __le32 [usertype] nsmagic
   security/commoncap.c:456:33: sparse:     got unsigned int [usertype]
   security/commoncap.c:457:29: sparse: sparse: restricted __le32 degrades to integer
   security/commoncap.c:458:39: sparse: sparse: invalid assignment: |=
   security/commoncap.c:458:39: sparse:    left side has type restricted __le32
   security/commoncap.c:458:39: sparse:    right side has type int
   security/commoncap.c:460:42: sparse: sparse: cast from restricted __le32
   security/commoncap.c:1281:41: sparse: sparse: dubious: !x | y

vim +424 security/commoncap.c

   357	
   358	/*
   359	 * getsecurity: We are called for security.* before any attempt to read the
   360	 * xattr from the inode itself.
   361	 *
   362	 * This gives us a chance to read the on-disk value and convert it.  If we
   363	 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
   364	 *
   365	 * Note we are not called by vfs_getxattr_alloc(), but that is only called
   366	 * by the integrity subsystem, which really wants the unconverted values -
   367	 * so that's good.
   368	 */
   369	int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
   370				  bool alloc)
   371	{
   372		int size, ret;
   373		kuid_t kroot;
   374		__le32 nsmagic, magic;
   375		uid_t root, mappedroot;
   376		char *tmpbuf = NULL;
   377		struct vfs_cap_data *cap;
   378		struct vfs_ns_cap_data *nscap = NULL;
   379		struct dentry *dentry;
   380		struct user_namespace *fs_ns;
   381	
   382		if (strcmp(name, "capability") != 0)
   383			return -EOPNOTSUPP;
   384	
   385		dentry = d_find_any_alias(inode);
   386		if (!dentry)
   387			return -EINVAL;
   388	
   389		size = sizeof(struct vfs_ns_cap_data);
   390		ret = (int) vfs_getxattr_alloc(dentry, XATTR_NAME_CAPS,
   391					 &tmpbuf, size, GFP_NOFS);
   392		dput(dentry);
   393	
   394		if (ret < 0)
   395			return ret;
   396	
   397		fs_ns = inode->i_sb->s_user_ns;
   398		cap = (struct vfs_cap_data *) tmpbuf;
   399		if (is_v2header((size_t) ret, cap)) {
   400			root = 0;
   401		} else if (is_v3header((size_t) ret, cap)) {
   402			nscap = (struct vfs_ns_cap_data *) tmpbuf;
   403			root = le32_to_cpu(nscap->rootid);
   404		} else {
   405			size = -EINVAL;
   406			goto out_free;
   407		}
   408	
   409		kroot = make_kuid(fs_ns, root);
   410	
   411		/* If the root kuid maps to a valid uid in current ns, then return
   412		 * this as a nscap. */
   413		mappedroot = from_kuid(current_user_ns(), kroot);
   414		if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
   415			size = sizeof(struct vfs_ns_cap_data);
   416			if (alloc) {
   417				if (!nscap) {
   418					/* v2 -> v3 conversion */
   419					nscap = kzalloc(size, GFP_ATOMIC);
   420					if (!nscap) {
   421						size = -ENOMEM;
   422						goto out_free;
   423					}
 > 424					nsmagic = VFS_CAP_REVISION_3;
 > 425					magic = le32_to_cpu(cap->magic_etc);
   426					if (magic & VFS_CAP_FLAGS_EFFECTIVE)
   427						nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
   428					memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
   429					nscap->magic_etc = cpu_to_le32(nsmagic);
   430				} else {
   431					/* use allocated v3 buffer */
   432					tmpbuf = NULL;
   433				}
   434				nscap->rootid = cpu_to_le32(mappedroot);
   435				*buffer = nscap;
   436			}
   437			goto out_free;
   438		}
   439	
   440		if (!rootid_owns_currentns(kroot)) {
   441			size = -EOVERFLOW;
   442			goto out_free;
   443		}
   444	
   445		/* This comes from a parent namespace.  Return as a v2 capability */
   446		size = sizeof(struct vfs_cap_data);
   447		if (alloc) {
   448			if (nscap) {
   449				/* v3 -> v2 conversion */
   450				cap = kzalloc(size, GFP_ATOMIC);
   451				if (!cap) {
   452					size = -ENOMEM;
   453					goto out_free;
   454				}
   455				magic = VFS_CAP_REVISION_2;
   456				nsmagic = le32_to_cpu(nscap->magic_etc);
   457				if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
   458					magic |= VFS_CAP_FLAGS_EFFECTIVE;
   459				memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
   460				cap->magic_etc = cpu_to_le32(magic);
   461			} else {
   462				/* use unconverted v2 */
   463				tmpbuf = NULL;
   464			}
   465			*buffer = cap;
   466		}
   467	out_free:
   468		kfree(tmpbuf);
   469		return size;
   470	}
   471	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability

From: Tyler Hicks <code@tyhicks.com>
Date: 2021-01-22 18:38:51

On 2021-01-19 17:22:03, Miklos Szeredi wrote:

Prior to commit 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into
vfs_setxattr()") the translation of nscap->rootid did not take stacked
filesystems (overlayfs and ecryptfs) into account.

That patch fixed the overlay case, but made the ecryptfs case worse.

Thanks for sending a fix!

I know that you don't have an eCryptfs setup to test with but I'm at a
loss about how to test this from the userns/fscaps side of things. Do
you have a sequence of unshare/setcap/getcap commands that I can run on
a file inside of an eCryptfs mount to verify that the bug exists after
7c03e2cda4a5 and then again to verify that this patch fixes the bug?

Tyler

quoted hunk

Restore old the behavior for ecryptfs that existed before the overlayfs
fix.  This does not fix ecryptfs's handling of complex user namespace
setups, but it does make sure existing setups don't regress.

Reported-by: Eric W. Biederman <redacted>
Cc: Tyler Hicks <code@tyhicks.com>
Fixes: 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into vfs_setxattr()")
Signed-off-by: Miklos Szeredi <redacted>
---
 fs/ecryptfs/inode.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index e23752d9a79f..58d0f7187997 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c

@@ -1016,15 +1016,19 @@ ecryptfs_setxattr(struct dentry *dentry, struct inode *inode,
 {
 	int rc;
 	struct dentry *lower_dentry;
+	struct inode *lower_inode;
 
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
-	if (!(d_inode(lower_dentry)->i_opflags & IOP_XATTR)) {
+	lower_inode = d_inode(lower_dentry);
+	if (!(lower_inode->i_opflags & IOP_XATTR)) {
 		rc = -EOPNOTSUPP;
 		goto out;
 	}
-	rc = vfs_setxattr(lower_dentry, name, value, size, flags);
+	inode_lock(lower_inode);
+	rc = __vfs_setxattr_locked(lower_dentry, name, value, size, flags, NULL);
+	inode_unlock(lower_inode);
 	if (!rc && inode)
-		fsstack_copy_attr_all(inode, d_inode(lower_dentry));
+		fsstack_copy_attr_all(inode, lower_inode);
 out:
 	return rc;
 }

-- 
2.26.2

Re: [PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability

From: Miklos Szeredi <hidden>
Date: 2021-01-26 05:24:59

On Fri, Jan 22, 2021 at 7:31 PM Tyler Hicks [off-list ref] wrote:

On 2021-01-19 17:22:03, Miklos Szeredi wrote:

quoted

Prior to commit 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into
vfs_setxattr()") the translation of nscap->rootid did not take stacked
filesystems (overlayfs and ecryptfs) into account.

That patch fixed the overlay case, but made the ecryptfs case worse.

Thanks for sending a fix!

I know that you don't have an eCryptfs setup to test with but I'm at a
loss about how to test this from the userns/fscaps side of things. Do
you have a sequence of unshare/setcap/getcap commands that I can run on
a file inside of an eCryptfs mount to verify that the bug exists after
7c03e2cda4a5 and then again to verify that this patch fixes the bug?

You need two terminals:
$ = <USER>
# = root

$ unshare -Um
$ echo $$
<PID>
# echo "0 1000 1" > uid_map
# cp uid_map gid_map
# echo 1000 2000 1 >> uid_map
# echo 2000 3000 1 >> uid_map
# cat uid_map > /proc/<PID>/uid_map
# cat gid_map > /proc/<PID>/gid_map
$ mkdir ~/tmp ~/mnt
$ mount -t tmpfs tmpfs ~/tmp
$ pwd
/home/<USER>
# nsenter -t <PID> -m
# [setup ecryptfs on /home/<USER>/mnt using /home/<USER>/tmp]
$ cd ~/mnt
$ touch test
$ /sbin/setcap -n 1000 cap_dac_override+eip test
$ /sbin/getcap -n test
test = cap_dac_override+eip [rootid=1000]

Without the patch, I'm thinking that it will do a double translate and
end up with rootid=2000 in the user namespace, but I might well have
messed it up...

Let me know how this goes.

Thanks,
Miklos

Re: [PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability

From: Miklos Szeredi <hidden>
Date: 2021-01-26 05:25:08

On Mon, Jan 25, 2021 at 2:25 PM Miklos Szeredi [off-list ref] wrote:

On Fri, Jan 22, 2021 at 7:31 PM Tyler Hicks [off-list ref] wrote:

quoted

On 2021-01-19 17:22:03, Miklos Szeredi wrote:

quoted

Prior to commit 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into
vfs_setxattr()") the translation of nscap->rootid did not take stacked
filesystems (overlayfs and ecryptfs) into account.

That patch fixed the overlay case, but made the ecryptfs case worse.

Thanks for sending a fix!

I know that you don't have an eCryptfs setup to test with but I'm at a
loss about how to test this from the userns/fscaps side of things. Do
you have a sequence of unshare/setcap/getcap commands that I can run on
a file inside of an eCryptfs mount to verify that the bug exists after
7c03e2cda4a5 and then again to verify that this patch fixes the bug?

You need two terminals:
$ = <USER>
# = root

$ unshare -Um
$ echo $$
<PID>
# echo "0 1000 1" > uid_map

NOTE:  <USER> is assumed to have uid=1000, so this and following
"1000" values need to be fixed up if it's not the case.

Thanks,
Miklos

Re: [PATCH 1/2] ecryptfs: fix uid translation for setxattr on security.capability

From: Tyler Hicks <code@tyhicks.com>
Date: 2021-01-26 05:27:13

On 2021-01-25 14:25:38, Miklos Szeredi wrote:

On Fri, Jan 22, 2021 at 7:31 PM Tyler Hicks [off-list ref] wrote:

quoted

On 2021-01-19 17:22:03, Miklos Szeredi wrote:

quoted

Prior to commit 7c03e2cda4a5 ("vfs: move cap_convert_nscap() call into
vfs_setxattr()") the translation of nscap->rootid did not take stacked
filesystems (overlayfs and ecryptfs) into account.

That patch fixed the overlay case, but made the ecryptfs case worse.

Thanks for sending a fix!

I know that you don't have an eCryptfs setup to test with but I'm at a
loss about how to test this from the userns/fscaps side of things. Do
you have a sequence of unshare/setcap/getcap commands that I can run on
a file inside of an eCryptfs mount to verify that the bug exists after
7c03e2cda4a5 and then again to verify that this patch fixes the bug?

You need two terminals:
$ = <USER>
# = root

$ unshare -Um
$ echo $$
<PID>
# echo "0 1000 1" > uid_map
# cp uid_map gid_map
# echo 1000 2000 1 >> uid_map
# echo 2000 3000 1 >> uid_map
# cat uid_map > /proc/<PID>/uid_map
# cat gid_map > /proc/<PID>/gid_map
$ mkdir ~/tmp ~/mnt
$ mount -t tmpfs tmpfs ~/tmp
$ pwd
/home/<USER>
# nsenter -t <PID> -m
# [setup ecryptfs on /home/<USER>/mnt using /home/<USER>/tmp]
$ cd ~/mnt
$ touch test
$ /sbin/setcap -n 1000 cap_dac_override+eip test
$ /sbin/getcap -n test
test = cap_dac_override+eip [rootid=1000]

Without the patch, I'm thinking that it will do a double translate and
end up with rootid=2000 in the user namespace, but I might well have
messed it up...

Let me know how this goes.

Spot-on instructions. Thank you for taking the time to provide the
steps.

I was able to repro the bug and verify the fix. The change visually
looks good to me and it passed through the eCryptfs regression tests.

I've pushed it to the eCryptfs next branch and I plan to submit it to
Linus on Thursday. Thanks again!

Tyler

Thanks,
Miklos

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