Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1700516
| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v4 11/15] exec: Use secureexec for clearing pdeath_signal |
| Date | 2017-08-01 02:00 +0200 |
| Message-ID | <u9sLo-4eo-15@gated-at.bofh.it> (permalink) |
| References | <u9sLn-4eo-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Like dumpability, clearing pdeath_signal happens both in setup_new_exec()
and later in commit_creds(). The test in setup_new_exec() is different
from all other privilege comparisons, though: it is checking the new cred
(bprm) uid vs the old cred (current) euid. This appears to be a bug,
introduced by commit a6f76f23d297 ("CRED: Make execve() take advantage of
copy-on-write credentials"):
- if (bprm->e_uid != current_euid() ||
- bprm->e_gid != current_egid()) {
- set_dumpable(current->mm, suid_dumpable);
+ if (bprm->cred->uid != current_euid() ||
+ bprm->cred->gid != current_egid()) {
It was bprm euid vs current euid (and egids), but the effective got
dropped. Nothing in the exec flow changes bprm->cred->uid (nor gid).
The call traces are:
prepare_bprm_creds()
prepare_exec_creds()
prepare_creds()
memcpy(new_creds, old_creds, ...)
security_prepare_creds() (unimplemented by commoncap)
...
prepare_binprm()
bprm_fill_uid()
resets euid/egid to current euid/egid
sets euid/egid on bprm based on set*id file bits
security_bprm_set_creds()
cap_bprm_set_creds()
handle all caps-based manipulations
so this test is effectively a test of current_uid() vs current_euid(),
which is wrong, just like the prior dumpability tests were wrong.
The commit log says "Clear pdeath_signal and set dumpable on
certain circumstances that may not be covered by commit_creds()." This
may be meaning the earlier old euid vs new euid (and egid) test that
got changed.
Luckily, as with dumpability, this is all masked by commit_creds()
which performs old/new euid and egid tests and clears pdeath_signal.
And again, like dumpability, we should include LSM secureexec logic for
pdeath_signal clearing. For example, Smack goes out of its way to clear
pdeath_signal when it finds a secureexec condition.
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge@hallyn.com>
---
fs/exec.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index f9997ea6414e..708a72f93320 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1348,8 +1348,7 @@ void setup_new_exec(struct linux_binprm * bprm)
*/
current->mm->task_size = TASK_SIZE;
- if (!uid_eq(bprm->cred->uid, current_euid()) ||
- !gid_eq(bprm->cred->gid, current_egid())) {
+ if (bprm->secureexec) {
current->pdeath_signal = 0;
} else {
if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
--
2.7.4
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 02/15] exec: Correct comments about "point of no return" Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 10/15] exec: Use secureexec for setting dumpability Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 10/15] exec: Use secureexec for setting dumpability James Morris <jmorris@namei.org> - 2017-08-01 02:50 +0200
[PATCH v4 08/15] commoncap: Move cap_elevated calculation into bprm_set_creds Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 08/15] commoncap: Move cap_elevated calculation into bprm_set_creds Andy Lutomirski <luto@kernel.org> - 2017-08-01 15:50 +0200
[PATCH v4 11/15] exec: Use secureexec for clearing pdeath_signal Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 05/15] selinux: Refactor to remove bprm_secureexec hook Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 05/15] selinux: Refactor to remove bprm_secureexec hook James Morris <jmorris@namei.org> - 2017-08-01 02:50 +0200
Re: [PATCH v4 05/15] selinux: Refactor to remove bprm_secureexec hook Andy Lutomirski <luto@kernel.org> - 2017-08-01 15:30 +0200
[PATCH v4 09/15] LSM: drop bprm_secureexec hook Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 01/15] exec: Rename bprm->cred_prepared to called_set_creds Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 03/15] binfmt: Introduce secureexec flag Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 03/15] binfmt: Introduce secureexec flag Kees Cook <keescook@chromium.org> - 2017-08-01 02:30 +0200
Re: [PATCH v4 03/15] binfmt: Introduce secureexec flag James Morris <jmorris@namei.org> - 2017-08-01 02:50 +0200
[PATCH v4 06/15] smack: Refactor to remove bprm_secureexec hook Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 06/15] smack: Refactor to remove bprm_secureexec hook James Morris <jmorris@namei.org> - 2017-08-01 02:50 +0200
Re: [PATCH v4 06/15] smack: Refactor to remove bprm_secureexec hook Casey Schaufler <casey@schaufler-ca.com> - 2017-08-01 17:30 +0200
[PATCH v4 07/15] commoncap: Refactor to remove bprm_secureexec hook Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 04/15] apparmor: Refactor to remove bprm_secureexec hook Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 13/15] exec: Consolidate dumpability logic Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
[PATCH v4 12/15] smack: Remove redundant pdeath_signal clearing Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 12/15] smack: Remove redundant pdeath_signal clearing James Morris <jmorris@namei.org> - 2017-08-01 03:00 +0200
Re: [PATCH v4 12/15] smack: Remove redundant pdeath_signal clearing Casey Schaufler <casey@schaufler-ca.com> - 2017-08-01 17:30 +0200
[PATCH v4 15/15] exec: Consolidate pdeath_signal clearing Kees Cook <keescook@chromium.org> - 2017-08-01 02:00 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Kees Cook <keescook@chromium.org> - 2017-08-01 02:40 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec James Morris <jmorris@namei.org> - 2017-08-01 03:00 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Kees Cook <keescook@chromium.org> - 2017-08-01 05:10 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-01 07:20 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-01 07:20 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Kees Cook <keescook@chromium.org> - 2017-08-01 17:10 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-01 22:20 +0200
Re: [PATCH v4 00/15] exec: Use sane stack rlimit under secureexec Kees Cook <keescook@chromium.org> - 2017-08-01 23:10 +0200
csiph-web