[syzbot] [fs?] BUG: unable to handle kernel NULL pointer dereference in do_pagemap_scan

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 861deac3b092 Linux 6.7-rc7
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12bf6e26e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=298e57794135adf0
dashboard link: https://syzkaller.appspot.com/bug?extid=f9238a0a31f9b5603fef
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13f4fc81e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15997e81e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b1f4e427f08b/disk-861deac3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/81317757e796/vmlinux-861deac3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f9d2dcfac209/bzImage-861deac3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f9238a...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc00000000fe: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000007f0-0x00000000000007f7]
CPU: 0 PID: 5068 Comm: syz-executor316 Not tainted 6.7.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:mm_has_notifiers include/linux/mmu_notifier.h:282 [inline]
RIP: 0010:mmu_notifier_invalidate_range_start include/linux/mmu_notifier.h:455 [inline]
RIP: 0010:do_pagemap_scan+0xa89/0xcd0 fs/proc/task_mmu.c:2438
Code: 8d 41 b8 01 00 00 00 e8 c5 0b 57 ff 48 8b 5c 24 78 58 48 b8 00 00 00 00 00 fc ff df 48 8d bb f0 07 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f8 01 00 00 48 83 bb f0 07 00 00 00 0f 85 1d 01
RSP: 0018:ffffc9000425fcf0 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8167148e
RDX: 00000000000000fe RSI: ffffffff8accb1a0 RDI: 00000000000007f0
RBP: 0000000020ffc000 R08: 0000000000000000 R09: fffffbfff23e37d2
R10: ffffffff91f1be97 R11: 0000000000000000 R12: 000000000000230e
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS: 00005555564df380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005fdeb8 CR3: 00000000740db000 CR4: 0000000000350ef0
Call Trace:
<TASK>
do_pagemap_cmd+0x5e/0x80 fs/proc/task_mmu.c:2494
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f0993b4dbf9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe8cc5b718 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0993b4dbf9
RDX: 0000000020000180 RSI: 00000000c0606610 RDI: 0000000000000004
RBP: 00007f0993bc05f0 R08: 00007ffe8cc5b3c4 R09: 0000000000000006
R10: 0000000000000014 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mm_has_notifiers include/linux/mmu_notifier.h:282 [inline]
RIP: 0010:mmu_notifier_invalidate_range_start include/linux/mmu_notifier.h:455 [inline]
RIP: 0010:do_pagemap_scan+0xa89/0xcd0 fs/proc/task_mmu.c:2438
Code: 8d 41 b8 01 00 00 00 e8 c5 0b 57 ff 48 8b 5c 24 78 58 48 b8 00 00 00 00 00 fc ff df 48 8d bb f0 07 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 f8 01 00 00 48 83 bb f0 07 00 00 00 0f 85 1d 01
RSP: 0018:ffffc9000425fcf0 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8167148e
RDX: 00000000000000fe RSI: ffffffff8accb1a0 RDI: 00000000000007f0
RBP: 0000000020ffc000 R08: 0000000000000000 R09: fffffbfff23e37d2
R10: ffffffff91f1be97 R11: 0000000000000000 R12: 000000000000230e
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS: 00005555564df380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0993b80b00 CR3: 00000000740db000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
0: 8d 41 b8 lea -0x48(%rcx),%eax
3: 01 00 add %eax,(%rax)
5: 00 00 add %al,(%rax)
7: e8 c5 0b 57 ff call 0xff570bd1
c: 48 8b 5c 24 78 mov 0x78(%rsp),%rbx
11: 58 pop %rax
12: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
19: fc ff df
1c: 48 8d bb f0 07 00 00 lea 0x7f0(%rbx),%rdi
23: 48 89 fa mov %rdi,%rdx
26: 48 c1 ea 03 shr $0x3,%rdx
* 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2e: 0f 85 f8 01 00 00 jne 0x22c
34: 48 83 bb f0 07 00 00 cmpq $0x0,0x7f0(%rbx)
3b: 00
3c: 0f .byte 0xf
3d: 85 .byte 0x85
3e: 1d .byte 0x1d
3f: 01 .byte 0x1


---
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[Lizhi Xu]

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 861deac3b092

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 435b61054b5b..f547057f096b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2433,6 +2433,9 @@ static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)

/* Protection change for the range is going to happen. */
if (p.arg.flags & PM_SCAN_WP_MATCHING) {
+ if (IS_ERR_OR_NULL(mm))
+ return -EINVAL;
+
mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
mm, p.arg.start, p.arg.end);
mmu_notifier_invalidate_range_start(&range);

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+f9238a...@syzkaller.appspotmail.com

Tested on:

commit: 861deac3 Linux 6.7-rc7
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=165ad77ee80000

kernel config: https://syzkaller.appspot.com/x/.config?x=298e57794135adf0
dashboard link: https://syzkaller.appspot.com/bug?extid=f9238a0a31f9b5603fef
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12250a09e80000

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