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Message-ID: <87poatfwg6.fsf@linutronix.de> Date: Thu, 14 Sep 2017 11:42:17 +0200 From: John Ogness <john.ogness@...utronix.de> To: Andy Lutomirski <luto@...nel.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>, Kees Cook <keescook@...omium.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Linux API <linux-api@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, Tycho Andersen <tycho.andersen@...onical.com>, Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org, stable@...r.kernel.org Subject: [PATCH] fs/proc: report eip/esp in /prod/PID/stat for coredumping Commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in /proc/PID/stat") stopped reporting eip/esp because it is racey and dangerous for executing tasks. The comment adds: As far as I know, there are no use programs that make any material use of these fields, so just get rid of them. However, existing userspace core-dump-handler applications (for example, minicoredumper) are using these fields since they provide an excellent cross-platform interface to these valuable pointers. So that commit introduced a user space visible regression. Partially revert the change and make the readout possible for tasks with the proper permissions and only if the target task has the PF_DUMPCORE flag set. Reported-by: Marco Felsch <marco.felsch@...h.de> Signed-off-by: John Ogness <john.ogness@...utronix.de> Cc: stable@...r.kernel.org Fixes: 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in> /proc/PID/stat") --- fs/proc/array.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/proc/array.c b/fs/proc/array.c index 88c3555..696cc68 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -421,7 +421,15 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, * esp and eip are intentionally zeroed out. There is no * non-racy way to read them without freezing the task. * Programs that need reliable values can use ptrace(2). + * + * The only exception is if the task is core dumping because + * 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_DUMPCORE)) { + eip = KSTK_EIP(task); + esp = KSTK_ESP(task); + } } get_task_comm(tcomm, task); -- 1.7.10.4
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