Hi! On Thu 07-11-19 10:54:10, syzbot wrote: > syzbot found the following crash on: > > HEAD commit: c68c5373 Add linux-next specific files for 20191107 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=13d6bcfce00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=742545dcdea21726 > dashboard link: https://syzkaller.appspot.com/bug?extid=991400e8eba7e00a26e1 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1529829ae00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16a55c0ce00000 > > The bug was bisected to: > > commit b1b4705d54abedfd69dcdf42779c521aa1e0fbd3 > Author: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx> > Date: Tue Nov 5 12:01:37 2019 +0000 > > ext4: introduce direct I/O read using iomap infrastructure Hum, interesting and from the first looks the problem looks real. Deciphered reproducer is: int fd0 = open("./file0", O_RDWR | O_CREAT | O_EXCL | O_DIRECT, 0); int fd1 = open("./file0, O_RDONLY); write(fd0, "some_data...", 512); sendfile(fd0, fd1, NULL, 0x7fffffa7); -> this is interesting as it will result in reading data from 'file0' at offset X with buffered read and writing them with direct write to offset X+512. So this way we'll grow the file up to those ~2GB in 512-byte chunks. - not sure if we ever get there but the remainder of the reproducer is: fd2 = open("./file0", O_RDWR | O_CREAT | O_NOATIME | O_SYNC, 0); sendfile(fd2, fd0, NULL, 0xffffffff) -> doesn't seem too interesting as fd0 is at EOF so this shouldn't do anything. Matthew, can you have a look? Honza > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1176cffae00000 > final crash: https://syzkaller.appspot.com/x/report.txt?x=1376cffae00000 > console output: https://syzkaller.appspot.com/x/log.txt?x=1576cffae00000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+991400e8eba7e00a26e1@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: b1b4705d54ab ("ext4: introduce direct I/O read using iomap > infrastructure") > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 8715 at lib/iov_iter.c:1162 iov_iter_pipe+0x25b/0x2f0 > lib/iov_iter.c:1162 > Kernel panic - not syncing: panic_on_warn set ... > CPU: 1 PID: 8715 Comm: syz-executor719 Not tainted 5.4.0-rc6-next-20191107 > #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+0x197/0x210 lib/dump_stack.c:118 > panic+0x2e3/0x75c kernel/panic.c:221 > __warn.cold+0x2f/0x35 kernel/panic.c:582 > report_bug+0x289/0x300 lib/bug.c:195 > fixup_bug arch/x86/kernel/traps.c:174 [inline] > fixup_bug arch/x86/kernel/traps.c:169 [inline] > do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267 > do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286 > invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027 > RIP: 0010:iov_iter_pipe+0x25b/0x2f0 lib/iov_iter.c:1162 > Code: 83 c0 03 38 d0 7c 04 84 d2 75 33 44 89 63 24 48 83 c4 10 5b 41 5c 41 > 5d 41 5e 41 5f 5d c3 e8 ac ba 2e fe 0f 0b e8 a5 ba 2e fe <0f> 0b e9 53 fe ff > ff 4c 89 f7 e8 46 e5 6a fe e9 f5 fd ff ff e8 dc > RSP: 0018:ffff8880a0b4f988 EFLAGS: 00010293 > RAX: ffff88808f1602c0 RBX: ffff8880a0b4fa18 RCX: ffffffff8344ac89 > RDX: 0000000000000000 RSI: ffffffff8344ae3b RDI: 0000000000000004 > RBP: ffff8880a0b4f9c0 R08: ffff88808f1602c0 R09: 0000000000000000 > R10: fffffbfff1390168 R11: ffffffff89c80b47 R12: ffff88808f121c00 > R13: 0000000000000010 R14: ffff88808f121cc8 R15: ffff88808f121cd0 > generic_file_splice_read+0xa7/0x800 fs/splice.c:303 > do_splice_to+0x127/0x180 fs/splice.c:877 > splice_direct_to_actor+0x2d3/0x970 fs/splice.c:955 > do_splice_direct+0x1da/0x2a0 fs/splice.c:1064 > do_sendfile+0x597/0xd00 fs/read_write.c:1464 > __do_sys_sendfile64 fs/read_write.c:1525 [inline] > __se_sys_sendfile64 fs/read_write.c:1511 [inline] > __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511 > do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x446969 > Code: e8 4c b4 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 > 0f 83 0b 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f05c41b8ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 > RAX: ffffffffffffffda RBX: 00000000006dbc58 RCX: 0000000000446969 > RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005 > RBP: 00000000006dbc50 R08: 0000000000000000 R09: 0000000000000000 > R10: 00000000ffffffff R11: 0000000000000246 R12: 00000000006dbc5c > R13: 00007fffb77353df R14: 00007f05c41b99c0 R15: 20c49ba5e353f7cf > Kernel Offset: disabled > Rebooting in 86400 seconds.. > > > --- > This bug is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
