Commit-ID: 451eb3f2053ea4eeb40f94947c542cfbd7636186 Gitweb: http://git.kernel.org/tip/451eb3f2053ea4eeb40f94947c542cfbd7636186 Author: John Ogness <john.ogness@xxxxxxxxxxxxx> AuthorDate: Thu, 14 Sep 2017 11:42:17 +0200 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Fri, 15 Sep 2017 23:04:59 +0200 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. Fixes: 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in> /proc/PID/stat") Reported-by: Marco Felsch <marco.felsch@xxxxxxx> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx> Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Tycho Andersen <tycho.andersen@xxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Linux API <linux-api@xxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/87poatfwg6.fsf@xxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> --- 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); -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
