On Mon, Dec 30, 2024 at 11:17:30AM +0100, Nam Cao wrote:
The field "eip" (instruction pointer) and "esp" (stack pointer) of a task can be read from /proc/PID/stat. These fields can be interesting for coredump.
However, these fields were disabled by commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in /proc/PID/stat"), because it is generally unsafe to do so. But it is safe for a coredumping process, and therefore exceptions were made:
for a coredumping thread by commit fd7d56270b52 ("fs/proc: Report eip/esp in /prod/PID/stat for coredumping").
for all other threads in a coredumping process by commit cb8f381f1613 ("fs/proc/array.c: allow reporting eip/esp for all coredumping threads").
The above two commits check the PF_DUMPCORE flag to determine a coredump thread and the PF_EXITING flag for the other threads.
Unfortunately, commit 92307383082d ("coredump: Don't perform any cleanups before dumping core") moved coredump to happen earlier and before PF_EXITING is set. Thus, checking PF_EXITING is no longer the correct way to determine threads in a coredumping process.
Instead of PF_EXITING, use PF_POSTCOREDUMP to determine the other threads.
Checking of PF_EXITING was added for coredumping, so it probably can now be removed. But it doesn't hurt to keep.
Fixes: 92307383082d ("coredump: Don't perform any cleanups before dumping core") Cc: stable@vger.kernel.org Cc: Eric W. Biederman ebiederm@xmission.com Acked-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Nam Cao namcao@linutronix.de
Thanks for fixing this!
Acked-by: Kees Cook kees@kernel.org