KASAN: slab-out-of-bounds Read in anon_vma_interval_tree_insert

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17c5801bb00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=387e564bc1c787b2ddc5
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+387e56...@syzkaller.appspotmail.com

Sensor A: Test Pattern: 75% Colorbar
Sensor A: Vertical Flip: false
Sensor A: Horizontal Flip: false
Sensor A: ================== END STATUS ==================
==================================================================
BUG: KASAN: slab-out-of-bounds in __anon_vma_interval_tree_insert mm/interval_tree.c:72 [inline]
BUG: KASAN: slab-out-of-bounds in anon_vma_interval_tree_insert+0x313/0x3d0 mm/interval_tree.c:83
Read of size 8 at addr ffff8880b0142218 by task syz-executor.2/8137

CPU: 1 PID: 8137 Comm: syz-executor.2 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
__anon_vma_interval_tree_insert mm/interval_tree.c:72 [inline]
anon_vma_interval_tree_insert+0x313/0x3d0 mm/interval_tree.c:83
anon_vma_chain_link mm/rmap.c:144 [inline]
anon_vma_clone+0x23f/0x5e0 mm/rmap.c:279
anon_vma_fork+0x82/0x630 mm/rmap.c:332
dup_mmap kernel/fork.c:504 [inline]
dup_mm kernel/fork.c:1285 [inline]
copy_mm kernel/fork.c:1341 [inline]
copy_process.part.0+0x360f/0x8260 kernel/fork.c:1913
copy_process kernel/fork.c:1710 [inline]
_do_fork+0x22f/0xf30 kernel/fork.c:2219
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f07a216048b
Code: ed 0f 85 60 01 00 00 64 4c 8b 0c 25 10 00 00 00 45 31 c0 4d 8d 91 d0 02 00 00 31 d2 31 f6 bf 11 00 20 01 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 89 00 00 00 41 89 c5 85 c0 0f 85 90 00 00
RSP: 002b:00007fff1ae86fa0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f07a216048b
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000555557438400
R10: 00005555574386d0 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 0000000000000001 R15: 00007fff1ae87080

Allocated by task 8134:
kmem_cache_alloc+0x122/0x370 mm/slab.c:3559
anon_vma_chain_alloc mm/rmap.c:129 [inline]
anon_vma_clone+0xe0/0x5e0 mm/rmap.c:269
anon_vma_fork+0x82/0x630 mm/rmap.c:332
dup_mmap kernel/fork.c:504 [inline]
dup_mm kernel/fork.c:1285 [inline]
copy_mm kernel/fork.c:1341 [inline]
copy_process.part.0+0x360f/0x8260 kernel/fork.c:1913
copy_process kernel/fork.c:1710 [inline]
_do_fork+0x22f/0xf30 kernel/fork.c:2219
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 17152:
__cache_free mm/slab.c:3503 [inline]
kmem_cache_free+0x7f/0x260 mm/slab.c:3765
anon_vma_chain_free mm/rmap.c:134 [inline]
unlink_anon_vmas+0x2a4/0x840 mm/rmap.c:401
free_pgtables+0xe2/0x2f0 mm/memory.c:638
exit_mmap+0x2c8/0x530 mm/mmap.c:3094
__mmput kernel/fork.c:1016 [inline]
mmput+0x14e/0x4a0 kernel/fork.c:1037
exit_mm kernel/exit.c:549 [inline]
do_exit+0xaec/0x2be0 kernel/exit.c:857
do_group_exit+0x125/0x310 kernel/exit.c:967
get_signal+0x3f2/0x1f70 kernel/signal.c:2589
do_signal+0x8f/0x1670 arch/x86/kernel/signal.c:799
exit_to_usermode_loop+0x204/0x2a0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880b01421c0
which belongs to the cache anon_vma_chain of size 80
The buggy address is located 8 bytes to the right of
80-byte region [ffff8880b01421c0, ffff8880b0142210)
The buggy address belongs to the page:
page:ffffea0002c05080 count:1 mapcount:0 mapping:ffff88823b833640 index:0x0
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffffea0002960348 ffffea0002653a48 ffff88823b833640
raw: 0000000000000000 ffff8880b0142000 0000000100000024 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880b0142100: 00 00 00 00 00 00 fc fc fc fc fb fb fb fb fb fb
ffff8880b0142180: fb fb fb fb fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8880b0142200: fb fb fc fc fc fc 00 00 00 00 00 00 00 00 00 00
^
ffff8880b0142280: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fc fc
ffff8880b0142300: fc fc fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================
Sensor A: ================= START STATUS =================
Sensor A: Test Pattern: 75% Colorbar
Sensor A: Vertical Flip: false
Sensor A: Horizontal Flip: false
Sensor A: ================== END STATUS ==================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.