syzbot


KASAN: use-after-free Read in ext4_find_extent

Status: upstream: reported C repro on 2023/06/18 03:55
Bug presence: origin:lts
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+466b2a18226770691edf@syzkaller.appspotmail.com
First crash: 413d, last: 39d
Cause bisection: failed (error log, bisect log)
  
Bug presence (2)
Date Name Commit Repro Result
2023/09/10 lts (merge base) b1644a0031cf C [report] KASAN: use-after-free Read in ext4_find_extent
2023/09/10 upstream (ToT) 535a265d7f0d C Didn't crash
Similar bugs (8)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in ext4_find_extent ext4 C error inconclusive 21 23d 570d 0/2 upstream: reported C repro on 2022/12/26 07:59
linux-5.15 KASAN: use-after-free Read in ext4_find_extent origin:lts-only C inconclusive 4 70d 365d 0/3 upstream: reported C repro on 2023/07/19 14:49
upstream KASAN: use-after-free Read in ext4_find_extent ext4 2 1002d 1063d 0/27 auto-closed as invalid on 2022/02/17 05:19
linux-6.1 KASAN: use-after-free Read in ext4_find_extent origin:upstream missing-backport C done 1 80d 303d 0/3 upstream: reported C repro on 2023/09/19 00:11
android-5-15 KASAN: use-after-free Read in ext4_find_extent ext4 origin:lts C error 9 1d15h 570d 0/2 upstream: reported C repro on 2022/12/26 07:59
upstream KASAN: use-after-free Read in ext4_find_extent (2) ext4 C error 2 440d 565d 22/27 fixed on 2023/06/08 14:41
upstream KASAN: use-after-free Read in ext4_find_extent (3) prio:low ext4 C error done 31 205d 387d 26/27 fixed on 2024/01/30 23:26
android-54 KASAN: slab-out-of-bounds Read in ext4_find_extent ext4 C 1 384d 570d 0/2 auto-obsoleted due to no activity on 2023/10/08 03:20
Last patch testing requests (4)
Created Duration User Patch Repo Result
2024/06/09 02:19 5m retest repro android14-6.1 report log
2024/03/21 02:25 5m retest repro android14-6.1 report log
2023/12/28 16:41 5m retest repro android14-6.1 report log
2023/10/11 08:05 8m retest repro android14-6.1 report log
Fix bisection attempts (7)
Created Duration User Patch Repo Result
2024/05/26 01:28 45m bisect fix android14-6.1 OK (0) job log log
2024/04/21 13:26 1h01m bisect fix android14-6.1 OK (0) job log log
2024/03/07 01:33 44m bisect fix android14-6.1 OK (0) job log log
2024/01/30 09:33 51m bisect fix android14-6.1 OK (0) job log log
2023/12/14 15:32 57m bisect fix android14-6.1 OK (0) job log log
2023/11/13 06:10 43m bisect fix android14-6.1 OK (0) job log log
2023/07/29 10:09 1h31m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbab/0xdb0 fs/ext4/extents.c:953
Read of size 4 at addr ffff8881218f0788 by task kworker/u4:0/8

CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 6.1.25-syzkaller-00088-gcd94fe67fd33 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x158/0x4e0 mm/kasan/report.c:427
 kasan_report+0x13c/0x170 mm/kasan/report.c:531
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0xbab/0xdb0 fs/ext4/extents.c:953
 ext4_ext_map_blocks+0x255/0x71e0 fs/ext4/extents.c:4103
 ext4_map_blocks+0xa42/0x1ce0 fs/ext4/inode.c:651
 mpage_map_one_extent fs/ext4/inode.c:2421 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline]
 ext4_writepages+0x17b5/0x3fd0 fs/ext4/inode.c:2842
 do_writepages+0x385/0x620 mm/page-writeback.c:2472
 __writeback_single_inode+0xdc/0xb80 fs/fs-writeback.c:1590
 writeback_sb_inodes+0xb33/0x18f0 fs/fs-writeback.c:1881
 wb_writeback+0x3b9/0x9f0 fs/fs-writeback.c:2055
 wb_do_writeback fs/fs-writeback.c:2198 [inline]
 wb_workfn+0x399/0x1030 fs/fs-writeback.c:2238
 process_one_work+0x73d/0xcb0 kernel/workqueue.c:2296
 worker_thread+0xa60/0x1260 kernel/workqueue.c:2443
 kthread+0x26d/0x300 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004863c00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1218f0
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004863c48 ffffea0004863bc8 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x8140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO|__GFP_CMA), pid 261, tgid 261 (sshd), ts 17873501342, free_ts 17925146961
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x213/0x220 mm/page_alloc.c:2582
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2589
 get_page_from_freelist+0x2762/0x27f0 mm/page_alloc.c:4387
 __alloc_pages+0x3a1/0x780 mm/page_alloc.c:5664
 __folio_alloc+0x15/0x40 mm/page_alloc.c:5696
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 alloc_page_vma include/linux/gfp.h:283 [inline]
 do_anonymous_page mm/memory.c:4170 [inline]
 handle_pte_fault mm/memory.c:5049 [inline]
 __handle_mm_fault mm/memory.c:5193 [inline]
 handle_mm_fault+0x1fb0/0x2f40 mm/memory.c:5333
 do_user_addr_fault arch/x86/mm/fault.c:1363 [inline]
 handle_page_fault arch/x86/mm/fault.c:1504 [inline]
 exc_page_fault+0x3a6/0x6e0 arch/x86/mm/fault.c:1560
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:570
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1494 [inline]
 free_pcp_prepare mm/page_alloc.c:1568 [inline]
 free_unref_page_prepare+0x83d/0x850 mm/page_alloc.c:3486
 free_unref_page_list+0xf6/0x6c0 mm/page_alloc.c:3628
 release_pages+0xf7f/0xfe0 mm/swap.c:1055
 free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:314
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu mm/mmu_gather.c:261 [inline]
 tlb_finish_mmu+0x1e0/0x3f0 mm/mmu_gather.c:361
 unmap_region+0x2c1/0x310 mm/mmap.c:2389
 do_mas_align_munmap+0xd05/0x1400 mm/mmap.c:2654
 do_mas_munmap+0x23e/0x2b0 mm/mmap.c:2712
 __vm_munmap+0x263/0x3a0 mm/mmap.c:3002
 __do_sys_munmap mm/mmap.c:3028 [inline]
 __se_sys_munmap mm/mmap.c:3024 [inline]
 __x64_sys_munmap+0x6b/0x80 mm/mmap.c:3024
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
 ffff8881218f0680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881218f0700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881218f0780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff8881218f0800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881218f0880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/inode.c:2433!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8 Comm: kworker/u4:0 Tainted: G    B              6.1.25-syzkaller-00088-gcd94fe67fd33 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: writeback wb_workfn (flush-7:0)
RIP: 0010:mpage_map_one_extent fs/ext4/inode.c:2433 [inline]
RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline]
RIP: 0010:ext4_writepages+0x3d6f/0x3fd0 fs/ext4/inode.c:2842
Code: e8 a6 f9 81 ff be 00 10 00 00 48 c7 c7 10 e3 cb 86 4c 89 f2 e8 02 5d ab 00 e9 0f fb ff ff e8 88 f9 81 ff 0f 0b e8 81 f9 81 ff <0f> 0b e8 da 9d 01 03 65 8b 05 db 30 0f 7e 41 89 c7 4c 89 f8 48 c1
RSP: 0018:ffffc90000087000 EFLAGS: 00010293
RAX: ffffffff81f2e06f RBX: dffffc0000000000 RCX: ffff88810037e540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000087410 R08: ffffffff81f2bd7f R09: ffffed10200ad24b
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888100569290 R15: ffffc900000872e0
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc64833d68 CR3: 00000001225e0000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_writepages+0x385/0x620 mm/page-writeback.c:2472
 __writeback_single_inode+0xdc/0xb80 fs/fs-writeback.c:1590
 writeback_sb_inodes+0xb33/0x18f0 fs/fs-writeback.c:1881
 wb_writeback+0x3b9/0x9f0 fs/fs-writeback.c:2055
 wb_do_writeback fs/fs-writeback.c:2198 [inline]
 wb_workfn+0x399/0x1030 fs/fs-writeback.c:2238
 process_one_work+0x73d/0xcb0 kernel/workqueue.c:2296
 worker_thread+0xa60/0x1260 kernel/workqueue.c:2443
 kthread+0x26d/0x300 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mpage_map_one_extent fs/ext4/inode.c:2433 [inline]
RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline]
RIP: 0010:ext4_writepages+0x3d6f/0x3fd0 fs/ext4/inode.c:2842
Code: e8 a6 f9 81 ff be 00 10 00 00 48 c7 c7 10 e3 cb 86 4c 89 f2 e8 02 5d ab 00 e9 0f fb ff ff e8 88 f9 81 ff 0f 0b e8 81 f9 81 ff <0f> 0b e8 da 9d 01 03 65 8b 05 db 30 0f 7e 41 89 c7 4c 89 f8 48 c1
RSP: 0018:ffffc90000087000 EFLAGS: 00010293
RAX: ffffffff81f2e06f RBX: dffffc0000000000 RCX: ffff88810037e540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000087410 R08: ffffffff81f2bd7f R09: ffffed10200ad24b
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888100569290 R15: ffffc900000872e0
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020006000 CR3: 000000010e83f000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/09/10 15:50 android14-6.1 cd94fe67fd33 6654cf89 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2023/06/18 03:48 android14-6.1 35fe0d393f80 f3921d4d .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
2023/06/01 08:26 android14-6.1 78fe8913d1b2 babc4389 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in ext4_find_extent
* Struck through repros no longer work on HEAD.