On Wed, Nov 14, 2018 at 2:36 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > On Wed, 2018-11-14 at 07:40 +1100, NeilBrown wrote: >> 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 /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ Hi Neil, Please include the Reported-by tag next time. I see the linux-next patch is already update, so let's tell syzbot that this is fixed here: #syz fix: fs/locks: always delete_block after waiting. If the bug is still open on syzbot dashboard: https://syzkaller.appspot.com#upstream syzbot will not report new bugs in these functions in future. Thanks >> > > 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; >> } > > That makes sense. I went ahead and squashed this patch into the earlier > one and pushed the result to my locks-next branch. linux-next should > pick it up soon. > > Thanks! > -- > Jeff Layton <jlayton@xxxxxxxxxx> > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/b49e02d54460c79c4e5472983f6b9390005881b8.camel%40kernel.org. > For more options, visit https://groups.google.com/d/optout.
