KASAN: null-ptr-deref Read in drop_buffers

Status: auto-obsoleted due to no activity on 2023/02/27 02:04
Subsystems: kernfs
[Documentation on labels]
Reported-by: syzbot+fbdb4ec578ebdcfb9ed2@syzkaller.appspotmail.com
First crash: 1414d, last: 1383d
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] fs/buffer: fix a NULL pointer dereference in drop_buffers() 5 (5) 2022/11/18 08:29
[syzbot] KASAN: null-ptr-deref Read in drop_buffers 0 (1) 2022/10/30 02:04
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: null-ptr-deref Read in drop_buffers (5) prio:high fs 11 14 60d 276d 0/29 upstream: reported on 2025/11/10 12:38
upstream KASAN: null-ptr-deref Read in drop_buffers (2) jfs 11 syz, C error 252 896d 1107d 0/29 auto-obsoleted due to no activity on 2024/05/08 22:28
upstream KASAN: null-ptr-deref Read in drop_buffers (4) fs 17 228 352d 360d 0/29 auto-obsoleted due to no activity on 2025/10/15 13:15
linux-6.1 KASAN: null-ptr-deref Read in drop_buffers 11 1 71d 71d 0/3 upstream: reported on 2026/06/03 12:36
upstream KASAN: null-ptr-deref Read in drop_buffers (3) fs 17 syz, C 98 514d 680d 0/29 auto-obsoleted due to no activity on 2025/06/08 23:43
linux-6.1 KASAN: slab-out-of-bounds Read in drop_buffers 17 1 558d 558d 0/3 auto-obsoleted due to no activity on 2025/05/11 23:03
linux-6.1 KASAN: slab-out-of-bounds Read in drop_buffers (2) origin:lts-only 17 syz, C inconclusive 18 126d 328d 3/3 fixed on 2026/04/11 13:11

Sample crash report:
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: null-ptr-deref in buffer_busy fs/buffer.c:2856 [inline]
BUG: KASAN: null-ptr-deref in drop_buffers+0x61/0x2f0 fs/buffer.c:2868
Read of size 4 at addr 0000000000000060 by task syz-executor.5/24786

CPU: 0 PID: 24786 Comm: syz-executor.5 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_report+0xf1/0x220 mm/kasan/report.c:436
 kasan_report+0xfb/0x130 mm/kasan/report.c:495
 kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 buffer_busy fs/buffer.c:2856 [inline]
 drop_buffers+0x61/0x2f0 fs/buffer.c:2868
 try_to_free_buffers+0x2b1/0x640 fs/buffer.c:2898
 shrink_page_list+0x3be3/0x6260 mm/vmscan.c:1939
 shrink_inactive_list+0x5cd/0xc10 mm/vmscan.c:2447
 shrink_list mm/vmscan.c:2674 [inline]
 shrink_lruvec+0x489/0xc80 mm/vmscan.c:2991
 shrink_node_memcgs+0x360/0x770 mm/vmscan.c:3180
 shrink_node+0xe9f/0x2040 mm/vmscan.c:3304
 shrink_zones+0x4fb/0xc40 mm/vmscan.c:3542
 do_try_to_free_pages+0x215/0xcd0 mm/vmscan.c:3601
 try_to_free_mem_cgroup_pages+0x3cb/0x6d0 mm/vmscan.c:3916
 memory_high_write+0x24f/0x3c0 mm/memcontrol.c:6303
 cgroup_file_write+0x2ab/0x780 kernel/cgroup/cgroup.c:3962
 kernfs_fop_write_iter+0x3ac/0x500 fs/kernfs/file.c:330
 do_iter_write+0x6f0/0xc50 fs/read_write.c:861
 iter_file_splice_write+0x830/0xff0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0xe6/0x1c0 fs/splice.c:931
 splice_direct_to_actor+0x4e4/0xc00 fs/splice.c:886
 do_splice_direct+0x2a0/0x3f0 fs/splice.c:974
 do_sendfile+0x641/0xfd0 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64+0x178/0x1e0 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f2ac848b5a9
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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2ac9545168 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f2ac85abf80 RCX: 00007f2ac848b5a9
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000007
RBP: 00007f2ac84e6580 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc10d5a64f R14: 00007f2ac9545300 R15: 0000000000022000
 </TASK>
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/10/16 13:06 upstream 55be6084c8e0 67cb024c .config console log report info ci-upstream-kasan-gce-smack-root KASAN: null-ptr-deref Read in drop_buffers
2022/10/30 02:04 upstream 200204f56f3b 2a71366b .config console log report info ci-qemu-upstream-386 KASAN: null-ptr-deref Read in drop_buffers
2022/10/29 01:39 upstream 200204f56f3b bc17b3a4 .config console log report info ci-qemu-upstream-386 KASAN: null-ptr-deref Read in drop_buffers
2022/10/18 00:19 upstream 9abf2313adc1 94744d21 .config console log report info ci-qemu-upstream-386 KASAN: null-ptr-deref Read in drop_buffers
2022/09/29 15:06 linux-next aaa11ce2ffc8 1d385642 .config console log report info [disk image] [vmlinux] ci-upstream-linux-next-kasan-gce-root KASAN: null-ptr-deref Read in drop_buffers
* Struck through repros no longer work on HEAD.