* FAILED: patch "[PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()" failed to apply to 5.15-stable tree
@ 2022-12-11 9:51 gregkh
2022-12-11 17:32 ` Jens Axboe
0 siblings, 1 reply; 3+ messages in thread
From: gregkh @ 2022-12-11 9:51 UTC (permalink / raw)
To: harshit.m.mogalapalli, axboe, syzkaller; +Cc: stable
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
Possible dependencies:
998b30c3948e ("io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()")
ed29b0b4fd83 ("io_uring: move to separate directory")
4c928904ff77 ("block: move CONFIG_BLOCK guard to top Makefile")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 998b30c3948e4d0b1097e639918c5cff332acac5 Mon Sep 17 00:00:00 2001
From: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Date: Tue, 6 Dec 2022 01:38:32 -0800
Subject: [PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()
Syzkaller reports a NULL deref bug as follows:
BUG: KASAN: null-ptr-deref in io_tctx_exit_cb+0x53/0xd3
Read of size 4 at addr 0000000000000138 by task file1/1955
CPU: 1 PID: 1955 Comm: file1 Not tainted 6.1.0-rc7-00103-gef4d3ea40565 #75
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xcd/0x134
? io_tctx_exit_cb+0x53/0xd3
kasan_report+0xbb/0x1f0
? io_tctx_exit_cb+0x53/0xd3
kasan_check_range+0x140/0x190
io_tctx_exit_cb+0x53/0xd3
task_work_run+0x164/0x250
? task_work_cancel+0x30/0x30
get_signal+0x1c3/0x2440
? lock_downgrade+0x6e0/0x6e0
? lock_downgrade+0x6e0/0x6e0
? exit_signals+0x8b0/0x8b0
? do_raw_read_unlock+0x3b/0x70
? do_raw_spin_unlock+0x50/0x230
arch_do_signal_or_restart+0x82/0x2470
? kmem_cache_free+0x260/0x4b0
? putname+0xfe/0x140
? get_sigframe_size+0x10/0x10
? do_execveat_common.isra.0+0x226/0x710
? lockdep_hardirqs_on+0x79/0x100
? putname+0xfe/0x140
? do_execveat_common.isra.0+0x238/0x710
exit_to_user_mode_prepare+0x15f/0x250
syscall_exit_to_user_mode+0x19/0x50
do_syscall_64+0x42/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0023:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:00000000fffb7790 EFLAGS: 00000200 ORIG_RAX: 000000000000000b
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Kernel panic - not syncing: panic_on_warn set ...
This happens because the adding of task_work from io_ring_exit_work()
isn't synchronized with canceling all work items from eg exec. The
execution of the two are ordered in that they are both run by the task
itself, but if io_tctx_exit_cb() is queued while we're canceling all
work items off exec AND gets executed when the task exits to userspace
rather than in the main loop in io_uring_cancel_generic(), then we can
find current->io_uring == NULL and hit the above crash.
It's safe to add this NULL check here, because the execution of the two
paths are done by the task itself.
Cc: stable@vger.kernel.org
Fixes: d56d938b4bef ("io_uring: do ctx initiated file note removal")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221206093833.3812138-1-harshit.m.mogalapalli@oracle.com
[axboe: add code comment and also put an explanation in the commit msg]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 8840cf3e20f2..61cd7ffd0f6a 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2707,8 +2707,10 @@ static __cold void io_tctx_exit_cb(struct callback_head *cb)
/*
* When @in_idle, we're in cancellation and it's racy to remove the
* node. It'll be removed by the end of cancellation, just ignore it.
+ * tctx can be NULL if the queueing of this task_work raced with
+ * work cancelation off the exec path.
*/
- if (!atomic_read(&tctx->in_idle))
+ if (tctx && !atomic_read(&tctx->in_idle))
io_uring_del_tctx_node((unsigned long)work->ctx);
complete(&work->completion);
}
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: FAILED: patch "[PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()" failed to apply to 5.15-stable tree
2022-12-11 9:51 FAILED: patch "[PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()" failed to apply to 5.15-stable tree gregkh
@ 2022-12-11 17:32 ` Jens Axboe
2022-12-12 8:04 ` Greg KH
0 siblings, 1 reply; 3+ messages in thread
From: Jens Axboe @ 2022-12-11 17:32 UTC (permalink / raw)
To: gregkh, harshit.m.mogalapalli, syzkaller; +Cc: stable
On 12/11/22 2:51?AM, gregkh@linuxfoundation.org wrote:
>
> The patch below does not apply to the 5.15-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
It does apply fine, but it's in fs/io_uring.c rather than
io_uring/io_uring.c as for the newer kernels. Attached one here that
just does the patch change and it applies witha a slight offset:
checking file fs/io_uring.c
Hunk #1 succeeded at 9467 (offset 6760 lines).
From 998b30c3948e4d0b1097e639918c5cff332acac5 Mon Sep 17 00:00:00 2001
From: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Date: Tue, 6 Dec 2022 01:38:32 -0800
Subject: [PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()
Syzkaller reports a NULL deref bug as follows:
BUG: KASAN: null-ptr-deref in io_tctx_exit_cb+0x53/0xd3
Read of size 4 at addr 0000000000000138 by task file1/1955
CPU: 1 PID: 1955 Comm: file1 Not tainted 6.1.0-rc7-00103-gef4d3ea40565 #75
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xcd/0x134
? io_tctx_exit_cb+0x53/0xd3
kasan_report+0xbb/0x1f0
? io_tctx_exit_cb+0x53/0xd3
kasan_check_range+0x140/0x190
io_tctx_exit_cb+0x53/0xd3
task_work_run+0x164/0x250
? task_work_cancel+0x30/0x30
get_signal+0x1c3/0x2440
? lock_downgrade+0x6e0/0x6e0
? lock_downgrade+0x6e0/0x6e0
? exit_signals+0x8b0/0x8b0
? do_raw_read_unlock+0x3b/0x70
? do_raw_spin_unlock+0x50/0x230
arch_do_signal_or_restart+0x82/0x2470
? kmem_cache_free+0x260/0x4b0
? putname+0xfe/0x140
? get_sigframe_size+0x10/0x10
? do_execveat_common.isra.0+0x226/0x710
? lockdep_hardirqs_on+0x79/0x100
? putname+0xfe/0x140
? do_execveat_common.isra.0+0x238/0x710
exit_to_user_mode_prepare+0x15f/0x250
syscall_exit_to_user_mode+0x19/0x50
do_syscall_64+0x42/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0023:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:00000000fffb7790 EFLAGS: 00000200 ORIG_RAX: 000000000000000b
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Kernel panic - not syncing: panic_on_warn set ...
This happens because the adding of task_work from io_ring_exit_work()
isn't synchronized with canceling all work items from eg exec. The
execution of the two are ordered in that they are both run by the task
itself, but if io_tctx_exit_cb() is queued while we're canceling all
work items off exec AND gets executed when the task exits to userspace
rather than in the main loop in io_uring_cancel_generic(), then we can
find current->io_uring == NULL and hit the above crash.
It's safe to add this NULL check here, because the execution of the two
paths are done by the task itself.
Cc: stable@vger.kernel.org
Fixes: d56d938b4bef ("io_uring: do ctx initiated file note removal")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221206093833.3812138-1-harshit.m.mogalapalli@oracle.com
[axboe: add code comment and also put an explanation in the commit msg]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 8840cf3e20f2..61cd7ffd0f6a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2707,8 +2707,10 @@ static __cold void io_tctx_exit_cb(struct callback_head *cb)
/*
* When @in_idle, we're in cancellation and it's racy to remove the
* node. It'll be removed by the end of cancellation, just ignore it.
+ * tctx can be NULL if the queueing of this task_work raced with
+ * work cancelation off the exec path.
*/
- if (!atomic_read(&tctx->in_idle))
+ if (tctx && !atomic_read(&tctx->in_idle))
io_uring_del_tctx_node((unsigned long)work->ctx);
complete(&work->completion);
}
--
Jens Axboe
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: FAILED: patch "[PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()" failed to apply to 5.15-stable tree
2022-12-11 17:32 ` Jens Axboe
@ 2022-12-12 8:04 ` Greg KH
0 siblings, 0 replies; 3+ messages in thread
From: Greg KH @ 2022-12-12 8:04 UTC (permalink / raw)
To: Jens Axboe; +Cc: harshit.m.mogalapalli, syzkaller, stable
On Sun, Dec 11, 2022 at 10:32:59AM -0700, Jens Axboe wrote:
> On 12/11/22 2:51?AM, gregkh@linuxfoundation.org wrote:
> >
> > The patch below does not apply to the 5.15-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
>
> It does apply fine, but it's in fs/io_uring.c rather than
> io_uring/io_uring.c as for the newer kernels. Attached one here that
> just does the patch change and it applies witha a slight offset:
>
Sorry, my fault, I should have caught this. Thanks for the backport!
greg k-h
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-12-12 8:04 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-12-11 9:51 FAILED: patch "[PATCH] io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()" failed to apply to 5.15-stable tree gregkh
2022-12-11 17:32 ` Jens Axboe
2022-12-12 8:04 ` Greg KH
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox