On Tue, Nov 13 2018, Jeff Layton wrote: > On Mon, 2018-11-12 at 12:34 -0800, syzbot wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: 442b8cea2477 Add linux-next specific files for 20181109 >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=115dbad5400000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=2f72bdb11df9fbe8 >> dashboard link: https://syzkaller.appspot.com/bug?extid=a4a3d526b4157113ec6a >> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >> >> Unfortunately, I don't have any reproducer for this crash yet. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+a4a3d526b4157113ec6a@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> device loop0 blocksize: 4096 >> __find_get_block_slow() failed. block=1, b_blocknr=8 >> b_state=0x00000029, b_size=512 >> device loop0 blocksize: 4096 >> ================================================================== >> BUG: KASAN: use-after-free in __list_del_entry_valid+0xf1/0x100 >> lib/list_debug.c:51 >> Read of size 8 at addr ffff88017eb47b70 by task syz-executor3/13461 >> >> CPU: 0 PID: 13461 Comm: syz-executor3 Not tainted 4.20.0-rc1-next-20181109+ >> #110 >> 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+0x244/0x39d lib/dump_stack.c:113 >> print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 >> kasan_report_error mm/kasan/report.c:354 [inline] >> kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412 >> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 >> __list_del_entry_valid+0xf1/0x100 lib/list_debug.c:51 >> __list_del_entry include/linux/list.h:117 [inline] >> list_del_init include/linux/list.h:159 [inline] >> __locks_delete_block fs/locks.c:683 [inline] >> locks_delete_block+0xce/0x3d0 fs/locks.c:716 >> locks_mandatory_area+0x48b/0x6a0 fs/locks.c:1398 >> rw_verify_area+0x2f2/0x360 fs/read_write.c:386 >> vfs_write+0x149/0x560 fs/read_write.c:544 >> ksys_write+0x101/0x260 fs/read_write.c:598 >> __do_sys_write fs/read_write.c:610 [inline] >> __se_sys_write fs/read_write.c:607 [inline] >> __x64_sys_write+0x73/0xb0 fs/read_write.c:607 >> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x457569 >> Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 >> RSP: 002b:00007ff2e8194c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 >> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569 >> RDX: 0000000000000010 RSI: 0000000020000180 RDI: 0000000000000006 >> RBP: 000000000072c0e0 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff2e81956d4 >> R13: 00000000004c571f R14: 00000000004d9360 R15: 00000000ffffffff >> >> The buggy address belongs to the page: >> page:ffffea0005fad1c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0 >> flags: 0x2fffc0000000000() >> raw: 02fffc0000000000 0000000000000000 ffffea0005fad1c8 0000000000000000 >> raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> >> Memory state around the buggy address: >> ffff88017eb47a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> ffff88017eb47a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> > ffff88017eb47b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> >> ^ >> ffff88017eb47b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> ffff88017eb47c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >> ================================================================== >> > > Ouch, crash down in the mandatory locking code. This is with Neil's set > from last week. I haven't merged the series he sent the other day yet, > but they don't seem to be different in this regard. > > Looks like the fl_blocked list might have had an entry on it that was > freed without being removed? locks_mandatory_area declares a file_lock > on the stack, but it seems to be initialized properly. > > The one weird thing is that locks_mandatory_area sets FL_ACCESS and > FL_SLEEP, but I don't see anything wrong with that right offhand. > > Neil, any thoughts? I'm not certain, but probably this: From: NeilBrown <neilb@xxxxxxxx> Date: Wed, 14 Nov 2018 07:38:05 +1100 Subject: [PATCH] fs/locks: always delete_block after waiting - mandatory locks The patch fs/locks: always delete_block after waiting. should have moved the locks_delete_block() call in locks_mandatory_area() too. This might fix the bug: Reported-by: syzbot+a4a3d526b4157113ec6a@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: NeilBrown <neilb@xxxxxxxx> --- fs/locks.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/locks.c b/fs/locks.c index f456cd3d9d50..eb0c0b33fb7b 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -1436,9 +1436,9 @@ int locks_mandatory_area(struct inode *inode, struct file *filp, loff_t start, continue; } - locks_delete_block(&fl); break; } + locks_delete_block(&fl); return error; } -- 2.14.0.rc0.dirty
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