Messages in this thread | | | Date | Wed, 20 Oct 2021 09:56:35 -0400 | From | Josef Bacik <> | Subject | Re: [PATCH -next] nbd: Fix use-after-free in pid_show |
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On Wed, Oct 20, 2021 at 03:39:59PM +0800, Ye Bin wrote: > I got issue as follows: > [ 263.886511] BUG: KASAN: use-after-free in pid_show+0x11f/0x13f > [ 263.888359] Read of size 4 at addr ffff8880bf0648c0 by task cat/746 > [ 263.890479] CPU: 0 PID: 746 Comm: cat Not tainted 4.19.90-dirty #140 > [ 263.893162] Call Trace: > [ 263.893509] dump_stack+0x108/0x15f > [ 263.893999] print_address_description+0xa5/0x372 > [ 263.894641] kasan_report.cold+0x236/0x2a8 > [ 263.895696] __asan_report_load4_noabort+0x25/0x30 > [ 263.896365] pid_show+0x11f/0x13f > [ 263.897422] dev_attr_show+0x48/0x90 > [ 263.898361] sysfs_kf_seq_show+0x24d/0x4b0 > [ 263.899479] kernfs_seq_show+0x14e/0x1b0 > [ 263.900029] seq_read+0x43f/0x1150 > [ 263.900499] kernfs_fop_read+0xc7/0x5a0 > [ 263.903764] vfs_read+0x113/0x350 > [ 263.904231] ksys_read+0x103/0x270 > [ 263.905230] __x64_sys_read+0x77/0xc0 > [ 263.906284] do_syscall_64+0x106/0x360 > [ 263.906797] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Reproduce this issue as follows: > 1. nbd-server 8000 /tmp/disk > 2. nbd-client localhost 8000 /dev/nbd1 > 3. cat /sys/block/nbd1/pid > Then trigger use-after-free in pid_show. > > Reason is after do step '2', nbd-client progress is already exit. So > it's task_struct already freed. > To solve this issue, revert part of 6521d39a64b3's modify and remove > useless 'recv_task' member of nbd_device. > > Fixes: 6521d39a64b3 ("nbd: Remove variable 'pid'") > Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Thanks,
Josef
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