[syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    15e7d45e786a Add linux-next specific files for 20241016
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1597745f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c36416f1c54640c0
dashboard link: https://syzkaller.appspot.com/bug?extid=65d101735df4bb19d2a3
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1623e830580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16582f27980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf2ad43c81cc/disk-15e7d45e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c85347a66a1c/vmlinux-15e7d45e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/648cf8e59c13/bzImage-15e7d45e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+65d101735df4bb19d2a3@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at include/linux/highmem.h:269!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 5238 Comm: syz-executor755 Not tainted 6.12.0-rc3-next-20241016-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:zero_user_segments include/linux/highmem.h:269 [inline]
RIP: 0010:folio_zero_range include/linux/highmem.h:641 [inline]
RIP: 0010:fuse_notify_store fs/fuse/dev.c:1671 [inline]
RIP: 0010:fuse_notify fs/fuse/dev.c:1908 [inline]
RIP: 0010:fuse_dev_do_write+0x5d6d/0x5da0 fs/fuse/dev.c:1992
Code: c6 a0 11 41 8c e8 43 fc c9 fe 90 0f 0b e8 ab 55 7e fe 4c 89 ef 48 c7 c6 40 11 41 8c e8 2c fc c9 fe 90 0f 0b e8 94 55 7e fe 90 <0f> 0b e8 8c 55 7e fe eb 0c e8 85 55 7e fe eb c1 e8 7e 55 7e fe 4c
RSP: 0018:ffffc90003e67860 EFLAGS: 00010293
RAX: ffffffff83168cbc RBX: 0000000000001001 RCX: ffff88802178bc00
RDX: 0000000000000000 RSI: 0000000000001001 RDI: 0000000000001000
RBP: ffffc90003e67bb0 R08: ffffffff8316685c R09: 1ffffd40003defd8
R10: dffffc0000000000 R11: fffff940003defd9 R12: 0000000000001000
R13: ffffea0001ef7ec0 R14: 1ffffd40003defd8 R15: 0000000000000001
FS:  000055557fdec380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001f80 CR3: 000000007a4ca000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 fuse_dev_write+0x148/0x1d0 fs/fuse/dev.c:2076
 new_sync_write fs/read_write.c:590 [inline]
 vfs_write+0xa6d/0xc90 fs/read_write.c:683
 ksys_write+0x183/0x2b0 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ffaa74606e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff9501f418 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffaa74a9029 RCX: 00007ffaa74606e9
RDX: 000000000000002a RSI: 0000000020001f80 RDI: 0000000000000003
RBP: 00007ffaa74d3610 R08: 00007fff9501f5e8 R09: 00007fff9501f5e8
R10: 0000000020000200 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff9501f5d8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:zero_user_segments include/linux/highmem.h:269 [inline]
RIP: 0010:folio_zero_range include/linux/highmem.h:641 [inline]
RIP: 0010:fuse_notify_store fs/fuse/dev.c:1671 [inline]
RIP: 0010:fuse_notify fs/fuse/dev.c:1908 [inline]
RIP: 0010:fuse_dev_do_write+0x5d6d/0x5da0 fs/fuse/dev.c:1992
Code: c6 a0 11 41 8c e8 43 fc c9 fe 90 0f 0b e8 ab 55 7e fe 4c 89 ef 48 c7 c6 40 11 41 8c e8 2c fc c9 fe 90 0f 0b e8 94 55 7e fe 90 <0f> 0b e8 8c 55 7e fe eb 0c e8 85 55 7e fe eb c1 e8 7e 55 7e fe 4c
RSP: 0018:ffffc90003e67860 EFLAGS: 00010293
RAX: ffffffff83168cbc RBX: 0000000000001001 RCX: ffff88802178bc00
RDX: 0000000000000000 RSI: 0000000000001001 RDI: 0000000000001000
RBP: ffffc90003e67bb0 R08: ffffffff8316685c R09: 1ffffd40003defd8
R10: dffffc0000000000 R11: fffff940003defd9 R12: 0000000000001000
R13: ffffea0001ef7ec0 R14: 1ffffd40003defd8 R15: 0000000000000001
FS:  000055557fdec380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055874a56a790 CR3: 000000007a4ca000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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Re: [syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[Hillf Danton]

On Sun, 20 Oct 2024 01:11:37 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    15e7d45e786a Add linux-next specific files for 20241016
> git tree:       linux-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16582f27980000

#syz test

--- x/fs/fuse/dev.c
+++ y/fs/fuse/dev.c
@@ -1668,7 +1668,7 @@ static int fuse_notify_store(struct fuse
 		err = fuse_copy_page(cs, &page, offset, this_num, 0);
 		if (!folio_test_uptodate(folio) && !err && offset == 0 &&
 		    (this_num == folio_size(folio) || file_size == end)) {
-			folio_zero_range(folio, this_num, folio_size(folio));
+			folio_zero_range(folio, this_num, folio_size(folio) - this_num);
 			folio_mark_uptodate(folio);
 		}
 		folio_unlock(folio);
--

Re: [syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[syzbot]

Hello,

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

Reported-by: syzbot+65d101735df4bb19d2a3@syzkaller.appspotmail.com
Tested-by: syzbot+65d101735df4bb19d2a3@syzkaller.appspotmail.com

Tested on:

commit:         f2493655 Add linux-next specific files for 20241018
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12852430580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=838d70a59aaad5d2
dashboard link: https://syzkaller.appspot.com/bug?extid=65d101735df4bb19d2a3
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1323825f980000

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

Re: [syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[syzbot]

syzbot has bisected this issue to:

commit 5d9e1455630d0f464f169bbd637dbb264cbd8ac8
Author: Josef Bacik <josef@toxicpanda.com>
Date:   Mon Sep 30 13:45:18 2024 +0000

    fuse: convert fuse_notify_store to use folios

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=120dc25f980000
start commit:   15e7d45e786a Add linux-next specific files for 20241016
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=110dc25f980000
console output: https://syzkaller.appspot.com/x/log.txt?x=160dc25f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c36416f1c54640c0
dashboard link: https://syzkaller.appspot.com/bug?extid=65d101735df4bb19d2a3
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1623e830580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16582f27980000

Reported-by: syzbot+65d101735df4bb19d2a3@syzkaller.appspotmail.com
Fixes: 5d9e1455630d ("fuse: convert fuse_notify_store to use folios")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [fuse?] kernel BUG in fuse_dev_do_write

[Hou Tao]

Hi,

On 10/21/2024 9:30 AM, syzbot wrote:
> syzbot has bisected this issue to:
>
> commit 5d9e1455630d0f464f169bbd637dbb264cbd8ac8
> Author: Josef Bacik <josef@toxicpanda.com>
> Date:   Mon Sep 30 13:45:18 2024 +0000
>
>     fuse: convert fuse_notify_store to use folios
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=120dc25f980000
> start commit:   15e7d45e786a Add linux-next specific files for 20241016
> git tree:       linux-next
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=110dc25f980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=160dc25f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c36416f1c54640c0
> dashboard link: https://syzkaller.appspot.com/bug?extid=65d101735df4bb19d2a3
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1623e830580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16582f27980000
>
> Reported-by: syzbot+65d101735df4bb19d2a3@syzkaller.appspotmail.com
> Fixes: 5d9e1455630d ("fuse: convert fuse_notify_store to use folios")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> .

It seems fuse_notify_store invokes folio_zero_range() incorrectly. The
third argument of folio_zero_range() should be the to-copy length
instead of the total length. The following patch will fix the problem:

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 5edad55750b0..87e39c9343c4 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1668,7 +1668,7 @@ static int fuse_notify_store(struct fuse_conn *fc,
unsigned int size,
                err = fuse_copy_page(cs, &page, offset, this_num, 0);
                if (!folio_test_uptodate(folio) && !err && offset == 0 &&
                    (this_num == folio_size(folio) || file_size == end)) {
-                       folio_zero_range(folio, this_num,
folio_size(folio));
+                       folio_zero_range(folio, this_num,
folio_size(folio) - this_num);
                        folio_mark_uptodate(folio);
                }
                folio_unlock(folio);

Will post a formal patch later.