From: "zhangyi (F)" <yi.zhang@huawei.com>
To: <gregkh@linuxfoundation.org>
Cc: <linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
<luto@kernel.org>, <adobriyan@gmail.com>,
<akpm@linux-foundation.org>, <vbabka@suse.cz>,
<peterz@infradead.org>, <bigeasy@linutronix.de>,
<mhocko@suse.com>, <john.ogness@linutronix.de>,
<yi.zhang@huawei.com>, <nixiaoming@huawei.com>
Subject: [PATCH 4.4 5/7] fs/proc: Report eip/esp in /prod/PID/stat for coredumping
Date: Mon, 2 Dec 2019 16:35:17 +0800 [thread overview]
Message-ID: <20191202083519.23138-6-yi.zhang@huawei.com> (raw)
In-Reply-To: <20191202083519.23138-1-yi.zhang@huawei.com>
From: John Ogness <john.ogness@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.felsch@preh.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Tycho Andersen <tycho.andersen@canonical.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: stable@vger.kernel.org
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linux API <linux-api@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/87poatfwg6.fsf@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ zhangyi: 68db0cf10678 does not merged, skip the task_stack.h for 4.4]
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
---
fs/proc/array.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 618c83f1866d..c3e1732bcaa5 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -429,7 +429,15 @@ 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);
--
2.17.2
next prev parent reply other threads:[~2019-12-02 8:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-02 8:35 [PATCH 4.4 0/7] fs/proc: Stop reporting eip and esp in zhangyi (F)
2019-12-02 8:35 ` [PATCH 4.4 1/7] sched/core: Allow putting thread_info into task_struct zhangyi (F)
2019-12-02 8:35 ` [PATCH 4.4 2/7] sched/core: Add try_get_task_stack() and put_task_stack() zhangyi (F)
2019-12-02 8:35 ` [PATCH 4.4 3/7] sched/core, x86: Make struct thread_info arch specific again zhangyi (F)
2019-12-02 8:35 ` [PATCH 4.4 4/7] fs/proc: Stop reporting eip and esp in /proc/PID/stat zhangyi (F)
2019-12-02 8:35 ` zhangyi (F) [this message]
2019-12-02 8:35 ` [PATCH 4.4 6/7] proc: fix coredump vs read /proc/*/stat race zhangyi (F)
2019-12-02 8:35 ` [PATCH 4.4 7/7] fs/proc/array.c: allow reporting eip/esp for all coredumping threads zhangyi (F)
2019-12-12 17:15 ` [PATCH 4.4 0/7] fs/proc: Stop reporting eip and esp in Greg KH
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