Re: [PATCH V3fix ghak120] audit: initialize context values in case of mandatory events
From: Paul Moore <paul@paul-moore.com>
Date: 2020-07-28 02:14:41
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On Mon, Jul 27, 2020 at 5:30 PM Richard Guy Briggs [off-list ref] wrote:
Issue ghak120 enabled syscall records to accompany required records when no rules are present to trigger the storage of syscall context. A reported issue showed that the cwd was not always initialized. That issue was already resolved ...
Yes and no. Yes, it appears to be resolved in v5.8-rc1 and above, but the problematic commit is in v5.7 and I'm not sure backporting the fix in v5.8-rcX plus this patch is the right thing to do for a released kernel. The lowest risk fix for v5.7 at this point is to do a revert; regardless of what happens with this patch and v5.8-rcX please post a revert for the audit/stable-5.7 tree as soon as you can.
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... but a review of all other records that could be triggered at the time of a syscall record revealed other potential values that could be missing or misleading. Initialize them. The fds array is reset to -1 after the first syscall to indicate it isn't valid any more, but was never set to -1 when the context was allocated to indicate it wasn't yet valid. The audit_inode* functions can be called without going through getname_flags() or getname_kernel() that sets audit_names and cwd, so set the cwd if it has not already been done so due to audit_names being valid. The LSM dump_common_audit_data() LSM_AUDIT_DATA_NET:AF_UNIX case was missed with the ghak96 patch, so add that case here. Please see issue https://github.com/linux-audit/audit-kernel/issues/120 Please see issue https://github.com/linux-audit/audit-kernel/issues/96 Passes audit-testsuite. Signed-off-by: Richard Guy Briggs <redacted> --- kernel/auditsc.c | 3 +++ security/lsm_audit.c | 1 + 2 files changed, 4 insertions(+)diff --git a/kernel/auditsc.c b/kernel/auditsc.c index 6884b50069d1..2f97618e6a34 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c@@ -929,6 +929,7 @@ static inline struct audit_context *audit_alloc_context(enum audit_state state) context->prio = state == AUDIT_RECORD_CONTEXT ? ~0ULL : 0; INIT_LIST_HEAD(&context->killed_trees); INIT_LIST_HEAD(&context->names_list); + context->fds[0] = -1; return context; }@@ -2076,6 +2077,7 @@ void __audit_inode(struct filename *name, const struct dentry *dentry, } handle_path(dentry); audit_copy_inode(n, dentry, inode, flags & AUDIT_INODE_NOEVAL); + _audit_getcwd(context); } void __audit_file(const struct file *file)@@ -2194,6 +2196,7 @@ void __audit_inode_child(struct inode *parent, audit_copy_inode(found_child, dentry, inode, 0); else found_child->ino = AUDIT_INO_UNSET; + _audit_getcwd(context); } EXPORT_SYMBOL_GPL(__audit_inode_child);diff --git a/security/lsm_audit.c b/security/lsm_audit.c index 53d0d183db8f..e93077612246 100644 --- a/security/lsm_audit.c +++ b/security/lsm_audit.c@@ -369,6 +369,7 @@ static void dump_common_audit_data(struct audit_buffer *ab, audit_log_untrustedstring(ab, p); else audit_log_n_hex(ab, p, len); + audit_getcwd(); break; } }
I understand the "fds[0] = -1" fix in audit_alloc_context() (ironically, the kzalloc() which is supposed to help with cases like this, hurts us with this particular field), but I'm still not quite seeing why we need to sprinkle audit_getcwd() calls everywhere to fix this bug (this seems more like a feature add than a bigfix). Yes, they may fix the problem but it seems like simply adding a context->pwd test in audit_log_name() similar to what we do in audit_log_exit() is the correct fix. We are currently at -rc7 and this really needs to land before v5.8 is released, presumably this weekend; this means a small and limited bug fix patch is what is needed. -- paul moore www.paul-moore.com