The patch titled Subject: fs/proc: do_task_stat: fix ESP not readable during coredump has been added to the -mm mm-hotfixes-unstable branch. Its filename is fs-proc-do_task_stat-fix-esp-not-readable-during-coredump.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Nam Cao namcao@linutronix.de Subject: fs/proc: do_task_stat: fix ESP not readable during coredump Date: Thu, 2 Jan 2025 09:22:56 +0100

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.

Link: https://lkml.kernel.org/r/d89af63d478d6c64cc46a01420b46fd6eb147d6f.173580577... Fixes: 92307383082d ("coredump: Don't perform any cleanups before dumping core") Signed-off-by: Nam Cao namcao@linutronix.de Acked-by: Oleg Nesterov oleg@redhat.com Acked-by: Kees Cook kees@kernel.org Cc: Eric W. Biederman ebiederm@xmission.com Cc: Dylan Hatch dylanbhatch@google.com Cc: John Ogness john.ogness@linutronix.de Cc: Shuah Khan shuah@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/proc/array.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/proc/array.c~fs-proc-do_task_stat-fix-esp-not-readable-during-coredump +++ a/fs/proc/array.c @@ -500,7 +500,7 @@ static int do_task_stat(struct seq_file * a program is not able to use ptrace(2) in that case. It is * safe because the task has stopped executing permanently. */ - if (permitted && (task->flags & (PF_EXITING|PF_DUMPCORE))) { + if (permitted && (task->flags & (PF_EXITING|PF_DUMPCORE|PF_POSTCOREDUMP))) { if (try_get_task_stack(task)) { eip = KSTK_EIP(task); esp = KSTK_ESP(task); _

Patches currently in -mm which might be from namcao@linutronix.de are

fs-proc-do_task_stat-fix-esp-not-readable-during-coredump.patch selftests-coredump-add-stackdump-test.patch