diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2019-01-03 15:28:07 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 13:13:47 -0800 |
| commit | 8099b047ecc431518b9bb6bdbba3549bbecdc343 (patch) | |
| tree | f0abafbb5f20984f92165e4da26fb37377dd497a /fs | |
| parent | fb5bf31722d0805a3f394f7d59f2e8cd07acccb7 (diff) | |
| download | lwn-8099b047ecc431518b9bb6bdbba3549bbecdc343.tar.gz lwn-8099b047ecc431518b9bb6bdbba3549bbecdc343.zip | |
exec: load_script: don't blindly truncate shebang string
load_script() simply truncates bprm->buf and this is very wrong if the
length of shebang string exceeds BINPRM_BUF_SIZE-2. This can silently
truncate i_arg or (worse) we can execute the wrong binary if buf[2:126]
happens to be the valid executable path.
Change load_script() to return ENOEXEC if it can't find '\n' or zero in
bprm->buf. Note that '\0' can come from either
prepare_binprm()->memset() or from kernel_read(), we do not care.
Link: http://lkml.kernel.org/r/20181112160931.GA28463@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ben Woodard <woodard@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/binfmt_script.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c index 7cde3f46ad26..d0078cbb718b 100644 --- a/fs/binfmt_script.c +++ b/fs/binfmt_script.c @@ -42,10 +42,14 @@ static int load_script(struct linux_binprm *bprm) fput(bprm->file); bprm->file = NULL; - bprm->buf[BINPRM_BUF_SIZE - 1] = '\0'; - if ((cp = strchr(bprm->buf, '\n')) == NULL) - cp = bprm->buf+BINPRM_BUF_SIZE-1; + for (cp = bprm->buf+2;; cp++) { + if (cp >= bprm->buf + BINPRM_BUF_SIZE) + return -ENOEXEC; + if (!*cp || (*cp == '\n')) + break; + } *cp = '\0'; + while (cp > bprm->buf) { cp--; if ((*cp == ' ') || (*cp == '\t')) |