linux-kernel - Re: [syzbot] [mm?] BUG: Bad page map (8)

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Message-ID: <0000000000001fa07f061d997826@google.com>
Date: Fri, 19 Jul 2024 06:14:02 -0700
From: syzbot <syzbot+ec4b7d82bb051330f15a@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] BUG: Bad page map (8)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: Bad page cache in process syz.NUM.NUM pfn:4a961

BUG: Bad page cache in process syz.0.15  pfn:4a961
page: refcount:4 mapcount:1 mapping:000000007efdb730 index:0x0 pfn:0x4a961
memcg:f8f00000073c6000
aops:shmem_aops ino:401
flags: 0x1ffc0000004002d(locked|referenced|uptodate|lru|swapbacked|node=0|zone=0|lastcpupid=0x7ff|kasantag=0x0)
raw: 01ffc0000004002d ffffc1ffc01bf9c8 ffffc1ffc038adc8 f0f00000061e6ab0
raw: 0000000000000000 0000000000000000 0000000400000000 f8f00000073c6000
page dumped because: still mapped when deleted
CPU: 1 PID: 3851 Comm: syz.0.15 Not tainted 6.10.0-rc7-syzkaller-00266-g4d145e3f830b-dirty #0
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace+0x94/0xec arch/arm64/kernel/stacktrace.c:317
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x78/0x90 lib/dump_stack.c:114
 dump_stack+0x18/0x24 lib/dump_stack.c:123
 filemap_unaccount_folio+0x118/0x278 mm/filemap.c:167
 __filemap_remove_folio+0x3c/0x178 mm/filemap.c:231
 filemap_remove_folio+0x48/0xa8 mm/filemap.c:264
 truncate_inode_folio+0x30/0x4c mm/truncate.c:195
 shmem_undo_range+0x208/0x620 mm/shmem.c:1012
 shmem_truncate_range mm/shmem.c:1125 [inline]
 shmem_evict_inode+0x130/0x2dc mm/shmem.c:1253
 evict+0xb4/0x198 fs/inode.c:667
 iput_final fs/inode.c:1741 [inline]
 iput fs/inode.c:1767 [inline]
 iput+0x100/0x1b8 fs/inode.c:1753
 dentry_unlink_inode+0xc0/0x188 fs/dcache.c:404
 __dentry_kill+0x7c/0x1d4 fs/dcache.c:607
 dput.part.0+0x30/0xbc fs/dcache.c:849
 dput+0x4c/0x50 fs/dcache.c:860
 __fput+0x110/0x2d4 fs/file_table.c:430
 ____fput+0x10/0x1c fs/file_table.c:450
 task_work_run+0x78/0xd0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 do_notify_resume+0x134/0x164 arch/arm64/kernel/entry-common.c:151
 exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
 el0_svc+0xc8/0xf8 arch/arm64/kernel/entry-common.c:713
 el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598
BUG: Bad page cache in process syz.0.15  pfn:4e2b7
page: refcount:4 mapcount:1 mapping:000000007efdb730 index:0x1 pfn:0x4e2b7
memcg:f8f00000073c6000
aops:shmem_aops ino:401
flags: 0x1ffc0000004002d(locked|referenced|uptodate|lru|swapbacked|node=0|zone=0|lastcpupid=0x7ff|kasantag=0x0)
raw: 01ffc0000004002d ffffc1ffc02a5848 ffffc1ffc02d1a88 f0f00000061e6ab0
raw: 0000000000000001 0000000000000000 0000000400000000 f8f00000073c6000
page dumped because: still mapped when deleted
CPU: 1 PID: 3851 Comm: syz.0.15 Tainted: G    B              6.10.0-rc7-syzkaller-00266-g4d145e3f830b-dirty #0
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace+0x94/0xec arch/arm64/kernel/stacktrace.c:317
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:324
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x78/0x90 lib/dump_stack.c:114
 dump_stack+0x18/0x24 lib/dump_stack.c:123
 filemap_unaccount_folio+0x118/0x278 mm/filemap.c:167
 __filemap_remove_folio+0x3c/0x178 mm/filemap.c:231
 filemap_remove_folio+0x48/0xa8 mm/filemap.c:264
 truncate_inode_folio+0x30/0x4c mm/truncate.c:195
 shmem_undo_range+0x208/0x620 mm/shmem.c:1012
 shmem_truncate_range mm/shmem.c:1125 [inline]
 shmem_evict_inode+0x130/0x2dc mm/shmem.c:1253
 evict+0xb4/0x198 fs/inode.c:667
 iput_final fs/inode.c:1741 [inline]
 iput fs/inode.c:1767 [inline]
 iput+0x100/0x1b8 fs/inode.c:1753
 dentry_unlink_inode+0xc0/0x188 fs/dcache.c:404
 __dentry_kill+0x7c/0x1d4 fs/dcache.c:607
 dput.part.0+0x30/0xbc fs/dcache.c:849
 dput+0x4c/0x50 fs/dcache.c:860
 __fput+0x110/0x2d4 fs/file_table.c:430
 ____fput+0x10/0x1c fs/file_table.c:450
 task_work_run+0x78/0xd0 kernel/task_work.c:180
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 do_notify_resume+0x134/0x164 arch/arm64/kernel/entry-common.c:151
 exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
 el0_svc+0xc8/0xf8 arch/arm64/kernel/entry-common.c:713
 el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598


Tested on:

commit:         4d145e3f Merge tag 'i2c-for-6.10-rc8' of git://git.ker..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14caa0ad980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6b5a15443200e31
dashboard link: https://syzkaller.appspot.com/bug?extid=ec4b7d82bb051330f15a
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10541fe1980000