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/fs-proc-do_task_stat-fix-esp-not-readable-during-coredump.patch
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@xxxxxxxxxxxxx>
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.1735805772.git.namcao@xxxxxxxxxxxxx
Fixes: 92307383082d ("coredump: Don't perform any cleanups before dumping core")
Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Kees Cook <kees@xxxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Dylan Hatch <dylanbhatch@xxxxxxxxxx>
Cc: John Ogness <john.ogness@xxxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxx are
fs-proc-do_task_stat-fix-esp-not-readable-during-coredump.patch
selftests-coredump-add-stackdump-test.patch
