4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: John Ogness <john.ogn...@linutronix.de>
commit fd7d56270b526ca3ed0c224362e3c64a0f86687a upstream.
Commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in
/proc/PID/stat") stopped reporting eip/esp because it is
racy 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.fel...@preh.de>
Signed-off-by: John Ogness <john.ogn...@linutronix.de>
Reviewed-by: Andy Lutomirski <l...@kernel.org>
Cc: Tycho Andersen <tycho.ander...@canonical.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Linux API <linux-...@vger.kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Link: http://lkml.kernel.org/r/87poatfwg6....@linutronix.de
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
fs/proc/array.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -60,6 +60,7 @@
#include <linux/tty.h>
#include <linux/string.h>
#include <linux/mman.h>
+#include <linux/sched.h>
#include <linux/proc_fs.h>
#include <linux/ioport.h>
#include <linux/uaccess.h>
@@ -416,7 +417,15 @@ static int do_task_stat(struct seq_file
* 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);
