[syzbot] KASAN: use-after-free Write in ext4_write_inline_data

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syzbot

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Aug 15, 2021, 12:27:18 PMAug 15
to adilger...@dilger.ca, bvana...@acm.org, linux...@vger.kernel.org, linux-...@vger.kernel.org, mi...@kernel.org, pet...@infradead.org, syzkall...@googlegroups.com, ty...@mit.edu
Hello,

syzbot found the following issue on:

HEAD commit: 761c6d7ec820 Merge tag 'arc-5.14-rc6' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=117755e9300000
kernel config: https://syzkaller.appspot.com/x/.config?x=e3a20bae04b96ccd
dashboard link: https://syzkaller.appspot.com/bug?extid=1bd003b0dbaa786227e6
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14fbbfe9300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124bbb81300000

The issue was bisected to:

commit 669de8bda87b92ab9a2fc663b3f5743c2ad1ae9f
Author: Bart Van Assche <bvana...@acm.org>
Date: Thu Feb 14 23:00:54 2019 +0000

kernel/workqueue: Use dynamic lockdep keys for workqueues

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17aa2665300000
final oops: https://syzkaller.appspot.com/x/report.txt?x=146a2665300000
console output: https://syzkaller.appspot.com/x/log.txt?x=106a2665300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1bd003...@syzkaller.appspotmail.com
Fixes: 669de8bda87b ("kernel/workqueue: Use dynamic lockdep keys for workqueues")

==================================================================
BUG: KASAN: use-after-free in memcpy include/linux/fortify-string.h:191 [inline]
BUG: KASAN: use-after-free in ext4_write_inline_data+0x30d/0x3e0 fs/ext4/inline.c:245
Write of size 70 at addr ffff8880359ec4ef by task syz-executor244/8446

CPU: 1 PID: 8446 Comm: syz-executor244 Not tainted 5.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
print_address_description.constprop.0.cold+0x6c/0x309 mm/kasan/report.c:233
__kasan_report mm/kasan/report.c:419 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:436
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
memcpy+0x39/0x60 mm/kasan/shadow.c:66
memcpy include/linux/fortify-string.h:191 [inline]
ext4_write_inline_data+0x30d/0x3e0 fs/ext4/inline.c:245
ext4_write_inline_data_end+0x24c/0x6b0 fs/ext4/inline.c:754
ext4_write_end+0x22b/0xf60 fs/ext4/inode.c:1290
ext4_da_write_end+0x440/0xb50 fs/ext4/inode.c:3079
generic_perform_write+0x2bd/0x500 mm/filemap.c:3667
ext4_buffered_write_iter+0x244/0x4d0 fs/ext4/file.c:269
ext4_file_write_iter+0x423/0x14e0 fs/ext4/file.c:680
call_write_iter include/linux/fs.h:2114 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x75a/0xa40 fs/read_write.c:605
ksys_write+0x12d/0x250 fs/read_write.c:658
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x44ac89
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:00007f8a10a6f2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004ce4e0 RCX: 000000000044ac89
RDX: 0000000000000082 RSI: 0000000020000180 RDI: 0000000000000008
RBP: 000000000049de98 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 024645fc87234f45 R14: 26e1d8b70aefbc5b R15: 00000000004ce4e8

The buggy address belongs to the page:
page:ffffea0000d67b00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x359ec
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000497f88 ffffea0000614208 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x400dc0(GFP_KERNEL_ACCOUNT|__GFP_ZERO), pid 8369, ts 45323892408, free_ts 45393497770
prep_new_page mm/page_alloc.c:2436 [inline]
get_page_from_freelist+0xa72/0x2f80 mm/page_alloc.c:4169
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5391
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2244
__pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
pte_alloc_one+0x16/0x230 arch/x86/mm/pgtable.c:33
do_fault_around mm/memory.c:4145 [inline]
do_read_fault mm/memory.c:4166 [inline]
do_fault mm/memory.c:4300 [inline]
handle_pte_fault mm/memory.c:4558 [inline]
__handle_mm_fault+0x49de/0x5320 mm/memory.c:4693
handle_mm_fault+0x1c8/0x790 mm/memory.c:4791
do_user_addr_fault+0x48b/0x11c0 arch/x86/mm/fault.c:1390
handle_page_fault arch/x86/mm/fault.c:1475 [inline]
exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1531
asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:568
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1346 [inline]
free_pcp_prepare+0x2c5/0x780 mm/page_alloc.c:1397
free_unref_page_prepare mm/page_alloc.c:3332 [inline]
free_unref_page_list+0x1a1/0x1050 mm/page_alloc.c:3448
release_pages+0x824/0x20b0 mm/swap.c:972
tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:242 [inline]
tlb_flush_mmu mm/mmu_gather.c:249 [inline]
tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:340
exit_mmap+0x1ea/0x620 mm/mmap.c:3203
__mmput+0x122/0x470 kernel/fork.c:1101
mmput+0x58/0x60 kernel/fork.c:1122
exit_mm kernel/exit.c:501 [inline]
do_exit+0xae2/0x2a60 kernel/exit.c:812
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address:
ffff8880359ec380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880359ec400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880359ec480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8880359ec500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8880359ec580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Theodore Ts'o

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Aug 21, 2021, 12:03:19 AMAug 21
to syzbot, adilger...@dilger.ca, bvana...@acm.org, linux...@vger.kernel.org, linux-...@vger.kernel.org, mi...@kernel.org, pet...@infradead.org, syzkall...@googlegroups.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git 9e445093e523f3277081314c864f708fd4bd34aa

syzbot

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Aug 21, 2021, 12:31:09 AMAug 21
to adilger...@dilger.ca, bvana...@acm.org, linux...@vger.kernel.org, linux-...@vger.kernel.org, mi...@kernel.org, pet...@infradead.org, syzkall...@googlegroups.com, ty...@mit.edu
Hello,

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

Reported-and-tested-by: syzbot+1bd003...@syzkaller.appspotmail.com

Tested on:

commit: 9e445093 ext4: fix race writing to an inline_data file..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
kernel config: https://syzkaller.appspot.com/x/.config?x=7273c75708b55890
dashboard link: https://syzkaller.appspot.com/bug?extid=1bd003b0dbaa786227e6
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1

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