Re: [syzbot] [fuse?] KASAN: null-ptr-deref Read in fuse_copy_do

[syzbot <syzbot+87b8e6ed25dbc41759f7@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in fuse_copy_do

fuse: *val=0000000000000000 buf=ffff88807d82c550, cs->write=0 op-code=15
------------[ cut here ]------------
kernel BUG at fs/fuse/dev.c:810!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 6694 Comm: syz.0.15 Not tainted 6.13.0-rc1-syzkaller-g4e968a4c8fcf #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:fuse_copy_do+0x334/0x3d0 fs/fuse/dev.c:810
Code: 74 05 e8 7f f8 f5 fe 8b 6b 3c e8 67 10 93 fe 8b 4c 24 0c 41 89 e8 4c 89 fe 48 8b 14 24 48 c7 c7 40 05 a9 8b e8 6d 48 72 fe 90 <0f> 0b 48 8b 7c 24 10 e8 50 f8 f5 fe e9 2e fd ff ff 48 89 df e8 43
RSP: 0018:ffffc90003407898 EFLAGS: 00010286
RAX: 0000000000000048 RBX: ffff8880249eb220 RCX: ffffffff81794fa9
RDX: 0000000000000000 RSI: ffffffff8179f976 RDI: 0000000000000005
RBP: 000000000000000f R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffffc90003407978
R13: ffffc90003407ca4 R14: ffffc90003407c60 R15: 0000000000000000
FS:  00007feebcbfe6c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000a000 CR3: 0000000037394000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 fuse_copy_one fs/fuse/dev.c:1072 [inline]
 fuse_copy_args+0x1e6/0x770 fs/fuse/dev.c:1090
 copy_out_args fs/fuse/dev.c:1973 [inline]
 fuse_dev_do_write+0x1cc1/0x3720 fs/fuse/dev.c:2059
 fuse_dev_write+0x14f/0x1e0 fs/fuse/dev.c:2094
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:679
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feebd97f2bf
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 8d 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 8e 02 00 48
RSP: 002b:00007feebcbfdfd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000020008380 RCX: 00007feebd97f2bf
RDX: 0000000000000015 RSI: 0000000020000540 RDI: 0000000000000003
RBP: 0000000000000050 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000293 R12: 0000000000000003
R13: 0000000020000c40 R14: 00007feebdb45fa0 R15: 00007fff5d43f8a8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fuse_copy_do+0x334/0x3d0 fs/fuse/dev.c:810
Code: 74 05 e8 7f f8 f5 fe 8b 6b 3c e8 67 10 93 fe 8b 4c 24 0c 41 89 e8 4c 89 fe 48 8b 14 24 48 c7 c7 40 05 a9 8b e8 6d 48 72 fe 90 <0f> 0b 48 8b 7c 24 10 e8 50 f8 f5 fe e9 2e fd ff ff 48 89 df e8 43
RSP: 0018:ffffc90003407898 EFLAGS: 00010286
RAX: 0000000000000048 RBX: ffff8880249eb220 RCX: ffffffff81794fa9
RDX: 0000000000000000 RSI: ffffffff8179f976 RDI: 0000000000000005
RBP: 000000000000000f R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffffc90003407978
R13: ffffc90003407ca4 R14: ffffc90003407c60 R15: 0000000000000000
FS:  00007feebcbfe6c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000a000 CR3: 0000000037394000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


Tested on:

commit:         4e968a4c debug folio conversion null ptr
git tree:       https://github.com/bsbernd/linux folio-syzbot-debug
console output: https://syzkaller.appspot.com/x/log.txt?x=114a2fc0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6851fe4f61792030
dashboard link: https://syzkaller.appspot.com/bug?extid=87b8e6ed25dbc41759f7
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.