[PATCH] exec: Weaken dumpability for secureexec

Kees Cook
2018-01-02T23:21:38Z

This is a logical revert of:

commit e37fdb785a5f ("exec: Use secureexec for setting dumpability")

This weakens dumpability back to checking only for uid/gid changes in
current (which is useless), but userspace depends on dumpability not
being tied to secureexec.

https://bugzilla.redhat.com/show_bug.cgi?id=1528633

Reported-by: Tom Horsley <horsley1953@gmail.com>
Fixes: e37fdb785a5f ("exec: Use secureexec for setting dumpability")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/exec.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 5688b5e1b937..7eb8d21bcab9 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1349,9 +1349,14 @@ void setup_new_exec(struct linux_binprm * bprm)

current->sas_ss_sp = current->sas_ss_size = 0;

- /* Figure out dumpability. */
+ /*
+ * Figure out dumpability. Note that this checking only of current
+ * is wrong, but userspace depends on it. This should be testing
+ * bprm->secureexec instead.
+ */
if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
- bprm->secureexec)
+ !(uid_eq(current_euid(), current_uid()) &&
+ gid_eq(current_egid(), current_gid())))
set_dumpable(current->mm, suid_dumpable);
else
set_dumpable(current->mm, SUID_DUMP_USER);
--
2.7.4

--
Kees Cook
Pixel Security