WARNING in af_alg_make_sg

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 763dede1 Merge tag 'for-linus-5.7-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b919c7e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=12205d036cec317f
dashboard link: https://syzkaller.appspot.com/bug?extid=3be1a33f04dc782e9fd5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=142f3b8fe00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159bd23fe00000

The bug was bisected to:

commit 4426e945df588f2878affddf88a51259200f7e29
Author: Peter Xu <pet...@redhat.com>
Date: Thu Apr 2 04:08:49 2020 +0000

mm/gup: allow VM_FAULT_RETRY for multiple times

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1408ea9fe00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=1608ea9fe00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1208ea9fe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+3be1a3...@syzkaller.appspotmail.com
Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times")

------------[ cut here ]------------
WARNING: CPU: 1 PID: 7094 at crypto/af_alg.c:404 af_alg_make_sg+0x399/0x400 crypto/af_alg.c:404
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7094 Comm: syz-executor037 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x35 kernel/panic.c:582
report_bug+0x27b/0x2f0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:175 [inline]
fixup_bug arch/x86/kernel/traps.c:170 [inline]
do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:af_alg_make_sg+0x399/0x400 crypto/af_alg.c:404
Code: 5c 24 2b 31 ff 89 de e8 c5 b9 f8 fd 84 db 74 0e e8 8c b8 f8 fd 48 8b 04 24 48 89 44 24 70 e8 7e b8 f8 fd 0f 0b e8 77 b8 f8 fd <0f> 0b c7 44 24 4c ea ff ff ff e9 4b ff ff ff 48 89 df e8 40 6e 36
RSP: 0018:ffffc900018779a0 EFLAGS: 00010293
RAX: ffff8880a16b65c0 RBX: ffff8880a4141220 RCX: ffffffff837a763d
RDX: 0000000000000000 RSI: ffffffff837a78f9 RDI: 0000000000000005
RBP: 000000001fef2254 R08: ffff8880a16b65c0 R09: ffffed10142d6cb9
R10: ffff8880a16b65c7 R11: ffffed10142d6cb8 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
hash_sendmsg+0x45c/0xad0 crypto/algif_hash.c:94
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6bf/0x7e0 net/socket.c:2362
___sys_sendmsg+0x100/0x170 net/socket.c:2416
__sys_sendmsg+0xec/0x1b0 net/socket.c:2449
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x446999
Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 5b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1427fb4d98 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000446999
RDX: 0000000000000000 RSI: 00000000200002c0 RDI: 0000000000000005
RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000068736168
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Hillf Danton]

On Wed, 08 Apr 2020 00:48:13 -0700

Make gup feed back correct error code in case of bailout.

--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1325,8 +1325,11 @@ retry:
* start trying again otherwise it can loop forever.
*/

- if (fatal_signal_pending(current))
+ if (fatal_signal_pending(current)) {
+ if (!pages_done)
+ pages_done = -EINTR;
break;
+ }

*locked = 1;
down_read(&mm->mmap_sem);

[Peter Xu]

CC Thomas too.

Sorry for all these mess...

Frankly speaking I didn't notice get_user_pages_fast() forbids
returning zero while __get_user_pages() allowed it... Ideally I think
the gup callers should check against ret>0 to know exactly how many
valid pages we've got, but it's not an excuse good enough...

Hillf, would you mind kick the syzbot directly next time when post the
fix? I'll make bold to do that for you this time, Thanks!

#syz test: #https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

8<--------------------------------------------------------------------
From 380003a56efc125565143c91ee6cefd7b3eba869 Mon Sep 17 00:00:00 2001
From: Hillf Danton <hda...@sina.com>
Date: Wed, 8 Apr 2020 11:01:25 -0400
Subject: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal
signal

__get_user_pages_locked() will return 0 instead of -EINTR after commit
4426e945df588 which added extra code to allow gup detect fatal signal
faster. Restore that behavior.

CC: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Hillf Danton <hda...@sina.com>
[peterx: write commit message]
Signed-off-by: Peter Xu <pet...@redhat.com>
---
mm/gup.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index afce0bc47e70..6076df8e04a4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1326,8 +1326,11 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,

* start trying again otherwise it can loop forever.
*/

- if (fatal_signal_pending(current))
+ if (fatal_signal_pending(current)) {
+ if (!pages_done)
+ pages_done = -EINTR;
break;
+ }

ret = down_read_killable(&mm->mmap_sem);
if (ret) {
--
2.24.1


--
Peter Xu

[syzbot]

"#https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git" does not look like a valid git repo address.

[Peter Xu]

I got one extra "#"... Doing it again...

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

[Michal Hocko]

On Wed 08-04-20 11:12:13, Peter Xu wrote:
> >From 380003a56efc125565143c91ee6cefd7b3eba869 Mon Sep 17 00:00:00 2001
> From: Hillf Danton <hda...@sina.com>
> Date: Wed, 8 Apr 2020 11:01:25 -0400
> Subject: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal
> signal
>
> __get_user_pages_locked() will return 0 instead of -EINTR after commit
> 4426e945df588 which added extra code to allow gup detect fatal signal
> faster. Restore that behavior.
>
> CC: Thomas Gleixner <tg...@linutronix.de>
> Signed-off-by: Hillf Danton <hda...@sina.com>
> [peterx: write commit message]

Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times")

> Signed-off-by: Peter Xu <pet...@redhat.com>

Acked-by: Michal Hocko <mho...@suse.com>

> ---
> mm/gup.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index afce0bc47e70..6076df8e04a4 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1326,8 +1326,11 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
> * start trying again otherwise it can loop forever.
> */
>
> - if (fatal_signal_pending(current))
> + if (fatal_signal_pending(current)) {
> + if (!pages_done)
> + pages_done = -EINTR;
> break;
> + }
>
> ret = down_read_killable(&mm->mmap_sem);
> if (ret) {
> --
> 2.24.1
>
>
> --
> Peter Xu
>

--
Michal Hocko
SUSE Labs

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+3be1a3...@syzkaller.appspotmail.com

Tested on:

commit: f5e94d10 Merge tag 'drm-next-2020-04-08' of git://anongit...
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
kernel config: https://syzkaller.appspot.com/x/.config?x=ca75979eeebf06c2

dashboard link: https://syzkaller.appspot.com/bug?extid=3be1a33f04dc782e9fd5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

patch: https://syzkaller.appspot.com/x/patch.diff?x=1672dcede00000

Note: testing is done by a robot and is best-effort only.

[Hillf Danton]

On Wed, 8 Apr 2020 17:31:14 +0200 Michal Hocko wrote:
>
> On Wed 08-04-20 11:12:13, Peter Xu wrote:

> > >From 380003a56efc125565143c91ee6cefd7b3eba869 Mon Sep 17 00:00:00 2001
> > From: Hillf Danton <hda...@sina.com>
> > Date: Wed, 8 Apr 2020 11:01:25 -0400
> > Subject: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal
> > signal
> >
> > __get_user_pages_locked() will return 0 instead of -EINTR after commit
> > 4426e945df588 which added extra code to allow gup detect fatal signal
> > faster. Restore that behavior.
> >
> > CC: Thomas Gleixner <tg...@linutronix.de>
> > Signed-off-by: Hillf Danton <hda...@sina.com>
> > [peterx: write commit message]
>

> Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times")

> > Signed-off-by: Peter Xu <pet...@redhat.com>
>
> Acked-by: Michal Hocko <mho...@suse.com>

Thank you, Sir.

Hillf