On 9/4/18 1:51 AM, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 217c3e019675 disable stringop truncation warnings for now > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13665da6400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=531a917630d2a492 > dashboard link: https://syzkaller.appspot.com/bug?extid=25dbecbec1e62c6b0dd4 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=163e910a400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=169dfe0a400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+25dbecbec1e62c6b0dd4@xxxxxxxxxxxxxxxxxxxxxxxxx > > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > divide error: 0000 [#1] SMP KASAN > CPU: 0 PID: 4667 Comm: syz-executor024 Not tainted 4.19.0-rc1+ #216 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:div_s64_rem include/linux/math64.h:41 [inline] > RIP: 0010:div_s64 include/linux/math64.h:139 [inline] > RIP: 0010:__nbd_ioctl drivers/block/nbd.c:1242 [inline] > RIP: 0010:nbd_ioctl+0x53c/0xcf0 drivers/block/nbd.c:1303 > Code: ea 03 80 3c 02 00 0f 85 1c 07 00 00 48 8b b5 c0 fe ff ff 48 63 8d b8 > fe ff ff 48 8b 86 c8 00 00 00 48 8d be c0 00 00 00 48 99 <48> f7 f9 48 ba > 00 00 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 80 3c > RSP: 0018:ffff8801c90bf828 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffff8801ccb23c00 RDI: ffff8801ccb23cc0 > RBP: ffff8801c90bf9a0 R08: ffff8801bc502640 R09: ffffed003a62d01d > R10: ffff8801c90bf818 R11: ffff8801d31680ef R12: ffff8801d3168000 > R13: 00000000ffffffe7 R14: ffff8801d31680e0 R15: ffff8801d5730840 > FS: 00000000015b2880(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000043e560 CR3: 00000001b8034000 CR4: 00000000001406f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > __blkdev_driver_ioctl block/ioctl.c:303 [inline] > blkdev_ioctl+0x9cd/0x2030 block/ioctl.c:601 > block_ioctl+0xee/0x130 fs/block_dev.c:1883 > vfs_ioctl fs/ioctl.c:46 [inline] > file_ioctl fs/ioctl.c:501 [inline] > do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685 > ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702 > __do_sys_ioctl fs/ioctl.c:709 [inline] > __se_sys_ioctl fs/ioctl.c:707 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707 > do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x443d29 > Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 7b d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007ffe343644d8 EFLAGS: 00000213 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000443d29 > RDX: 0000000000000000 RSI: 000000000000ab01 RDI: 0000000000000003 > RBP: 00000000006ce018 R08: 0000000000000000 R09: 00000000004002e0 > R10: 000000000000000f R11: 0000000000000213 R12: 0000000000401a30 > R13: 0000000000401ac0 R14: 0000000000000000 R15: 0000000000000000 > Modules linked in: > Dumping ftrace buffer: > (ftrace buffer empty) > ---[ end trace 25c60c4714d4e2ee ]--- > RIP: 0010:div_s64_rem include/linux/math64.h:41 [inline] > RIP: 0010:div_s64 include/linux/math64.h:139 [inline] > RIP: 0010:__nbd_ioctl drivers/block/nbd.c:1242 [inline] > RIP: 0010:nbd_ioctl+0x53c/0xcf0 drivers/block/nbd.c:1303 > Code: ea 03 80 3c 02 00 0f 85 1c 07 00 00 48 8b b5 c0 fe ff ff 48 63 8d b8 > fe ff ff 48 8b 86 c8 00 00 00 48 8d be c0 00 00 00 48 99 <48> f7 f9 48 ba > 00 00 00 00 00 fc ff df 48 89 f9 48 c1 e9 03 80 3c > RSP: 0018:ffff8801c90bf828 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: ffff8801ccb23c00 RDI: ffff8801ccb23cc0 > RBP: ffff8801c90bf9a0 R08: ffff8801bc502640 R09: ffffed003a62d01d > R10: ffff8801c90bf818 R11: ffff8801d31680ef R12: ffff8801d3168000 > R13: 00000000ffffffe7 R14: ffff8801d31680e0 R15: ffff8801d5730840 > FS: 00000000015b2880(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000043e560 CR3: 00000001b8034000 CR4: 00000000001406f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Looks like NBD_SET_BLKSIZE is happy to just take whatever value. We should ensure that it's a power of 2, not zero, and bigger or equal than 512, but smaller or equal to PAGE_SIZE. Something like this? diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 3863c00372bb..14a51254c3db 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1239,6 +1239,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, case NBD_SET_SOCK: return nbd_add_socket(nbd, arg, false); case NBD_SET_BLKSIZE: + if (!arg || !is_power_of_2(arg) || arg < 512 || + arg > PAGE_SIZE) + return -EINVAL; nbd_size_set(nbd, arg, div_s64(config->bytesize, arg)); return 0; -- Jens Axboe
