2024-03-21 20:04:23

by Justin Stitt

Subject: [PATCH v2] binfmt: replace deprecated strncpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

There is a _nearly_ identical implementation of fill_psinfo present in
binfmt_elf.c -- except that one uses get_task_comm over strncpy(). Let's
mirror that in binfmt_elf_fdpic.c

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://github.com/KSPP/linux/issues/90
Cc: [email protected]
Signed-off-by: Justin Stitt <[email protected]>
---
Changes in v2:
- use get_task_comm (thanks Eric)
- Link to v1: https://lore.kernel.org/r/20240321-strncpy-fs-binfmt_elf_fdpic-c-v1-1-fdde26c8989e@google.com
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
fs/binfmt_elf_fdpic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 1920ed69279b..3314249e8674 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -1359,7 +1359,7 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
SET_UID(psinfo->pr_uid, from_kuid_munged(cred->user_ns, cred->uid));
SET_GID(psinfo->pr_gid, from_kgid_munged(cred->user_ns, cred->gid));
rcu_read_unlock();
- strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname));
+ get_task_comm(psinfo->pr_fname, p);

return 0;
}

---
base-commit: a4145ce1e7bc247fd6f2846e8699473448717b37
change-id: 20240320-strncpy-fs-binfmt_elf_fdpic-c-828286d76310

Best regards,
--
Justin Stitt <[email protected]>

2024-03-22 03:31:07

by Kees Cook

Subject: Re: [PATCH v2] binfmt: replace deprecated strncpy

On Thu, 21 Mar 2024 20:04:08 +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> There is a _nearly_ identical implementation of fill_psinfo present in
> binfmt_elf.c -- except that one uses get_task_comm over strncpy(). Let's
> mirror that in binfmt_elf_fdpic.c
>
> [...]

Applied to for-next/execve, thanks!

[1/1] binfmt: replace deprecated strncpy
https://git.kernel.org/kees/c/5248f4097308

Take care,

--
Kees Cook