diff options
| author | Kees Cook <keescook@chromium.org> | 2022-10-18 00:17:24 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2022-10-25 15:17:08 -0700 |
| commit | 275498a98b1fe77deebddfc4f8986c0cf2c3ced7 (patch) | |
| tree | 1592dd1311d98d4ce94476d0209871e59fc32e93 /fs/exec.c | |
| parent | 23a7aea5faf6500051c52dfaba46845c41b3abd4 (diff) | |
exec: Add comments on check_unsafe_exec() fs counting
Add some comments about what the fs counting is doing in
check_unsafe_exec() and how it relates to the call graph.
Specifically, we can't force an unshare of the fs because
of at least Chrome:
https://lore.kernel.org/lkml/86CE201B-5632-4BB7-BCF6-7CB2C2895409@chromium.org/
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Link: https://lore.kernel.org/r/20221018071537.never.662-kees@kernel.org
Diffstat (limited to 'fs/exec.c')
| -rw-r--r-- | fs/exec.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c index 34e6a2e53268..b3e87bd50962 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1573,6 +1573,12 @@ static void check_unsafe_exec(struct linux_binprm *bprm) if (task_no_new_privs(current)) bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS; + /* + * If another task is sharing our fs, we cannot safely + * suid exec because the differently privileged task + * will be able to manipulate the current directory, etc. + * It would be nice to force an unshare instead... + */ t = p; n_fs = 1; spin_lock(&p->fs->lock); @@ -1753,6 +1759,7 @@ static int search_binary_handler(struct linux_binprm *bprm) return retval; } +/* binfmt handlers will call back into begin_new_exec() on success. */ static int exec_binprm(struct linux_binprm *bprm) { pid_t old_pid, old_vpid; @@ -1811,6 +1818,11 @@ static int bprm_execve(struct linux_binprm *bprm, if (retval) return retval; + /* + * Check for unsafe execution states before exec_binprm(), which + * will call back into begin_new_exec(), into bprm_creds_from_file(), + * where setuid-ness is evaluated. + */ check_unsafe_exec(bprm); current->in_execve = 1; |