4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
commit ada1986d07976d60bed5017aa38b7f7cf27883f7 upstream.
Alfred Agrell found that TOMOYO cannot handle execveat(AT_EMPTY_PATH)
inside chroot environment where /dev and /proc are not mounted, for
commit 51f39a1f0cea ("syscalls: implement execveat() system call") missed
that TOMOYO tries to canonicalize argv[0] when the filename fed to the
executed program as argv[0] is supplied using potentially nonexistent
pathname.
Since "/dev/fd/<fd>" already lost symlink information used for obtaining
that <fd>, it is too late to reconstruct symlink's pathname. Although
<filename> part of "/dev/fd/<fd>/<filename>" might not be canonicalized,
TOMOYO cannot use tomoyo_realpath_nofollow() when /dev or /proc is not
mounted. Therefore, fallback to tomoyo_realpath_from_path() when
tomoyo_realpath_nofollow() failed.
Reported-by: Alfred Agrell <blubban@xxxxxxxxx>
Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1082001
Fixes: 51f39a1f0cea ("syscalls: implement execveat() system call")
Cc: stable@xxxxxxxxxxxxxxx # v3.19+
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
security/tomoyo/domain.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/security/tomoyo/domain.c
+++ b/security/tomoyo/domain.c
@@ -701,10 +701,13 @@ int tomoyo_find_next_domain(struct linux
ee->r.obj = &ee->obj;
ee->obj.path1 = bprm->file->f_path;
/* Get symlink's pathname of program. */
- retval = -ENOENT;
exename.name = tomoyo_realpath_nofollow(original_name);
- if (!exename.name)
- goto out;
+ if (!exename.name) {
+ /* Fallback to realpath if symlink's pathname does not exist. */
+ exename.name = tomoyo_realpath_from_path(&bprm->file->f_path);
+ if (!exename.name)
+ goto out;
+ }
tomoyo_fill_path_info(&exename);
retry:
/* Check 'aggregator' directive. */
