[syzbot] general protection fault in ext4_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: daadb3bd0e8d Merge tag 'locking_core_for_v5.17_rc1' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=122fc6f7b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=ec2807b2e9360dbb
dashboard link: https://syzkaller.appspot.com/bug?extid=138c9e58e3cb22eae3b4
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+138c9e...@syzkaller.appspotmail.com

RBP: 00007f283db0b1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fffb1b01d5f R14: 00007f283db0b300 R15: 0000000000022000
</TASK>
general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]
CPU: 0 PID: 32175 Comm: syz-executor.3 Not tainted 5.16.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ext4_fill_super+0x240/0x770 fs/ext4/super.c:5551
Code: 3b 4c 89 6c 24 20 49 8d bd a8 06 00 00 be 2f 00 00 00 ba 21 00 00 00 e8 5e 6d d8 01 4d 8d af 90 00 00 00 4d 89 ec 49 c1 ec 03 <41> 80 3c 2c 00 74 08 4c 89 ef e8 11 4e 97 ff 49 c7 45 00 01 00 00
RSP: 0018:ffffc9000b5cfbe8 EFLAGS: 00010206
RAX: ffff8880234c46ac RBX: ffff888090bc7cf0 RCX: 0000000000040000
RDX: ffffc9000abd9000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: dffffc0000000000 R08: ffffffff8411122e R09: fffffbfff197f727
R10: fffffbfff197f727 R11: 0000000000000000 R12: 0000000000000012
R13: 0000000000000090 R14: ffff888071347b00 R15: 0000000000000000
FS: 00007f283db0b700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6db90cb558 CR3: 000000008fafc000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
get_tree_bdev+0x406/0x630 fs/super.c:1295
vfs_get_tree+0x86/0x270 fs/super.c:1500
do_new_mount fs/namespace.c:2994 [inline]
path_mount+0x1986/0x2c30 fs/namespace.c:3324
do_mount fs/namespace.c:3337 [inline]
__do_sys_mount fs/namespace.c:3545 [inline]
__se_sys_mount+0x308/0x3c0 fs/namespace.c:3522
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f283f195eb9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f283db0b168 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f283f2a8f60 RCX: 00007f283f195eb9
RDX: 0000000020000240 RSI: 0000000020000000 RDI: 0000000020000100
RBP: 00007f283db0b1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007fffb1b01d5f R14: 00007f283db0b300 R15: 0000000000022000
</TASK>
Modules linked in:
---[ end trace 2017ba6e0452af99 ]---
RIP: 0010:ext4_fill_super+0x240/0x770 fs/ext4/super.c:5551
Code: 3b 4c 89 6c 24 20 49 8d bd a8 06 00 00 be 2f 00 00 00 ba 21 00 00 00 e8 5e 6d d8 01 4d 8d af 90 00 00 00 4d 89 ec 49 c1 ec 03 <41> 80 3c 2c 00 74 08 4c 89 ef e8 11 4e 97 ff 49 c7 45 00 01 00 00
RSP: 0018:ffffc9000b5cfbe8 EFLAGS: 00010206
RAX: ffff8880234c46ac RBX: ffff888090bc7cf0 RCX: 0000000000040000
RDX: ffffc9000abd9000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: dffffc0000000000 R08: ffffffff8411122e R09: fffffbfff197f727
R10: fffffbfff197f727 R11: 0000000000000000 R12: 0000000000000012
R13: 0000000000000090 R14: ffff888071347b00 R15: 0000000000000000
FS: 00007f283db0b700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8eb615a718 CR3: 000000008fafc000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 3b 4c 89 6c cmp 0x6c(%rcx,%rcx,4),%ecx
4: 24 20 and $0x20,%al
6: 49 8d bd a8 06 00 00 lea 0x6a8(%r13),%rdi
d: be 2f 00 00 00 mov $0x2f,%esi
12: ba 21 00 00 00 mov $0x21,%edx
17: e8 5e 6d d8 01 callq 0x1d86d7a
1c: 4d 8d af 90 00 00 00 lea 0x90(%r15),%r13
23: 4d 89 ec mov %r13,%r12
26: 49 c1 ec 03 shr $0x3,%r12
* 2a: 41 80 3c 2c 00 cmpb $0x0,(%r12,%rbp,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 ef mov %r13,%rdi
34: e8 11 4e 97 ff callq 0xff974e4a
39: 49 rex.WB
3a: c7 .byte 0xc7
3b: 45 00 01 add %r8b,(%r9)


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 0457e5153e0e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146d12b4700000
kernel config: https://syzkaller.appspot.com/x/.config?x=cd57c0f940a9a1ec

dashboard link: https://syzkaller.appspot.com/bug?extid=138c9e58e3cb22eae3b4
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17f7004fb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=178cf108700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+138c9e...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]

CPU: 0 PID: 3603 Comm: syz-executor131 Not tainted 5.17.0-rc2-syzkaller-00316-g0457e5153e0e #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:ext4_fill_super+0x247/0x770 fs/ext4/super.c:5550
Code: 3b 4c 89 6c 24 20 49 8d bd a8 06 00 00 be 2f 00 00 00 ba 21 00 00 00 e8 87 5a d9 01 4d 8d af 90 00 00 00 4d 89 ec 49 c1 ec 03 <41> 80 3c 2c 00 74 08 4c 89 ef e8 ca 7d 96 ff 49 c7 45 00 01 00 00
RSP: 0018:ffffc9000284fbe8 EFLAGS: 00010206
RAX: ffff8880217dc6ac RBX: ffff88801c4048f0 RCX: ffff88807d4b9d00
RDX: 0000000000000000 RSI: 000000000000002f RDI: 0000000000000035
RBP: dffffc0000000000 R08: ffffffff84142d6e R09: fffffbfff197f79f
R10: fffffbfff197f79f R11: 0000000000000000 R12: 0000000000000012
R13: 0000000000000090 R14: ffff888014784f00 R15: 0000000000000000
FS: 00005555563943c0(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000000000 CR3: 000000001c361000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

get_tree_bdev+0x406/0x630 fs/super.c:1292
vfs_get_tree+0x86/0x270 fs/super.c:1497

do_new_mount fs/namespace.c:2994 [inline]
path_mount+0x1986/0x2c30 fs/namespace.c:3324
do_mount fs/namespace.c:3337 [inline]
__do_sys_mount fs/namespace.c:3545 [inline]
__se_sys_mount+0x308/0x3c0 fs/namespace.c:3522
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7fb3d4cbca49
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 15 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc0c4f4df8 EFLAGS: 00000246
ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fb3d4cbca49
RDX: 0000000020000100 RSI: 00000000200000c0 RDI: 0000000020000080
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000003636
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc0c4f4e00
R13: 00007ffc0c4f4ea0 R14: 00007ffc0c4f4e60 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_fill_super+0x247/0x770 fs/ext4/super.c:5550
Code: 3b 4c 89 6c 24 20 49 8d bd a8 06 00 00 be 2f 00 00 00 ba 21 00 00 00 e8 87 5a d9 01 4d 8d af 90 00 00 00 4d 89 ec 49 c1 ec 03 <41> 80 3c 2c 00 74 08 4c 89 ef e8 ca 7d 96 ff 49 c7 45 00 01 00 00
RSP: 0018:ffffc9000284fbe8 EFLAGS: 00010206

RAX: ffff8880217dc6ac RBX: ffff88801c4048f0 RCX: ffff88807d4b9d00
RDX: 0000000000000000 RSI: 000000000000002f RDI: 0000000000000035

----------------
Code disassembly (best guess):
0: 3b 4c 89 6c cmp 0x6c(%rcx,%rcx,4),%ecx
4: 24 20 and $0x20,%al
6: 49 8d bd a8 06 00 00 lea 0x6a8(%r13),%rdi
d: be 2f 00 00 00 mov $0x2f,%esi
12: ba 21 00 00 00 mov $0x21,%edx

17: e8 87 5a d9 01 callq 0x1d95aa3

1c: 4d 8d af 90 00 00 00 lea 0x90(%r15),%r13
23: 4d 89 ec mov %r13,%r12
26: 49 c1 ec 03 shr $0x3,%r12
* 2a: 41 80 3c 2c 00 cmpb $0x0,(%r12,%rbp,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 ef mov %r13,%rdi

34: e8 ca 7d 96 ff callq 0xff967e03

[syzbot]

syzbot has bisected this issue to:

commit cebe85d570cf84804e848332d6721bc9e5300e07
Author: Lukas Czerner <lcze...@redhat.com>
Date: Wed Oct 27 14:18:56 2021 +0000

ext4: switch to the new mount api

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14902978700000
start commit: 0457e5153e0e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=16902978700000
console output: https://syzkaller.appspot.com/x/log.txt?x=12902978700000

kernel config: https://syzkaller.appspot.com/x/.config?x=cd57c0f940a9a1ec
dashboard link: https://syzkaller.appspot.com/bug?extid=138c9e58e3cb22eae3b4

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17f7004fb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=178cf108700000

Reported-by: syzbot+138c9e...@syzkaller.appspotmail.com
Fixes: cebe85d570cf ("ext4: switch to the new mount api")

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

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+138c9e...@syzkaller.appspotmail.com

Tested on:

commit: ef6b3530 Add linux-next specific files for 20220204
git tree: linux-next
kernel config: https://syzkaller.appspot.com/x/.config?x=5278e9bfbaa88d84

dashboard link: https://syzkaller.appspot.com/bug?extid=138c9e58e3cb22eae3b4
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2

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

[Lukas Czerner]

I believe that this has been fixed with upstream commit

commit 7c268d4ce2d3761f666a9950b029c8902bfab710
Author: Lukas Czerner <lcze...@redhat.com>
Date: Wed Jan 19 14:02:09 2022 +0100

ext4: fix potential NULL pointer dereference in ext4_fill_super()

By mistake we fail to return an error from ext4_fill_super() in case
that ext4_alloc_sbi() fails to allocate a new sbi. Instead we just set
the ret variable and allow the function to continue which will later
lead to a NULL pointer dereference. Fix it by returning -ENOMEM in the
case ext4_alloc_sbi() fails.

Fixes: cebe85d570cf ("ext4: switch to the new mount api")

Reported-by: kernel test robot <l...@intel.com>
Reported-by: Dan Carpenter <dan.ca...@oracle.com>
Signed-off-by: Lukas Czerner <lcze...@redhat.com>
Link: https://lore.kernel.org/r/20220119130209....@redhat.com
Signed-off-by: Theodore Ts'o <ty...@mit.edu>
Cc: sta...@kernel.org

Thanks!
-Lukas

[Dmitry Vyukov]

Let's tell syzbot then:

#syz fix: ext4: fix potential NULL pointer dereference in ext4_fill_super()

Thanks