On Mon, Jul 29, 2024 at 10:27 PM [off-list ref] wrote:

From: Al Viro <viro@zeniv.linux.org.uk>

keep file reference through the entire thing, don't bother with
grabbing struct path reference (except, for now, around the LSM
call and that only until it gets constified) and while we are
at it, don't confuse the hell out of readers by random mix of
path.dentry->d_sb and path.mnt->mnt_sb uses - these two are equal,
so just put one of those into a local variable and use that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 kernel/bpf/token.c | 69 +++++++++++++++++-----------------------------
 1 file changed, 26 insertions(+), 43 deletions(-)

LGTM overall (modulo // comments, but see below)

Acked-by: Andrii Nakryiko <andrii@kernel.org>

[...]

-       err = security_bpf_token_create(token, attr, &path);
+       path_get(&path);        // kill it
+       err = security_bpf_token_create(token, attr, &path); // constify
+       path_put(&path);        // kill it
        if (err)
                goto out_token;

By constify you mean something like below?

commit 06a6442ca9cc441805881eea61fd57d7defadaca
Author: Andrii Nakryiko [off-list ref]
Date:   Tue Aug 6 15:38:12 2024 -0700

    security: constify struct path in bpf_token_create() LSM hook

    There is no reason why struct path pointer shouldn't be const-qualified
    when being passed into bpf_token_create() LSM hook. Add that const.

    Suggested-by: Al Viro [off-list ref]
    Signed-off-by: Andrii Nakryiko [off-list ref]

diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 855db460e08b..462b55378241 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h

@@ -431,7 +431,7 @@ LSM_HOOK(int, 0, bpf_prog_load, struct bpf_prog

*prog, union bpf_attr *attr,
      struct bpf_token *token)
 LSM_HOOK(void, LSM_RET_VOID, bpf_prog_free, struct bpf_prog *prog)
 LSM_HOOK(int, 0, bpf_token_create, struct bpf_token *token, union
bpf_attr *attr,
-     struct path *path)
+     const struct path *path)
 LSM_HOOK(void, LSM_RET_VOID, bpf_token_free, struct bpf_token *token)
 LSM_HOOK(int, 0, bpf_token_cmd, const struct bpf_token *token, enum
bpf_cmd cmd)
 LSM_HOOK(int, 0, bpf_token_capable, const struct bpf_token *token, int cap)

diff --git a/include/linux/security.h b/include/linux/security.h
index 1390f1efb4f0..31523a2c71c4 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h

@@ -2137,7 +2137,7 @@ extern int security_bpf_prog_load(struct

bpf_prog *prog, union bpf_attr *attr,
                   struct bpf_token *token);
 extern void security_bpf_prog_free(struct bpf_prog *prog);
 extern int security_bpf_token_create(struct bpf_token *token, union
bpf_attr *attr,
-                     struct path *path);
+                     const struct path *path);
 extern void security_bpf_token_free(struct bpf_token *token);
 extern int security_bpf_token_cmd(const struct bpf_token *token, enum
bpf_cmd cmd);
 extern int security_bpf_token_capable(const struct bpf_token *token, int cap);

@@ -2177,7 +2177,7 @@ static inline void security_bpf_prog_free(struct

bpf_prog *prog)
 { }

 static inline int security_bpf_token_create(struct bpf_token *token,
union bpf_attr *attr,
-                     struct path *path)
+                        const struct path *path)
 {
     return 0;
 }

diff --git a/security/security.c b/security/security.c
index 8cee5b6c6e6d..d8d0b67ced25 100644
--- a/security/security.c
+++ b/security/security.c

@@ -5510,7 +5510,7 @@ int security_bpf_prog_load(struct bpf_prog

*prog, union bpf_attr *attr,
  * Return: Returns 0 on success, error on failure.
  */
 int security_bpf_token_create(struct bpf_token *token, union bpf_attr *attr,
-                  struct path *path)
+                  const struct path *path)
 {
     return call_int_hook(bpf_token_create, token, attr, path);
 }

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 55c78c318ccd..0eec141a8f37 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c

@@ -6965,7 +6965,7 @@ static void selinux_bpf_prog_free(struct bpf_prog *prog)
 }

 static int selinux_bpf_token_create(struct bpf_token *token, union

bpf_attr *attr,
-                    struct path *path)
+                    const struct path *path)
 {
     struct bpf_security_struct *bpfsec;


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