[PATCH] exec: Weaken dumpability for secureexec

[Kees Cook <keescook@chromium.org>]

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