We met NULL pointer BUG as follow: [ 151.760358] BUG: unable to handle kernel NULL pointer dereference at 0000000000000060 [ 151.761340] PGD 80000001011eb067 P4D 80000001011eb067 PUD 1011ea067 PMD 0 [ 151.762039] Oops: 0000 [#1] SMP PTI [ 151.762406] Modules linked in: [ 151.762723] CPU: 2 PID: 3561 Comm: mdadm-test Kdump: loaded Not tainted 4.17.0-rc1+ #238 [ 151.763542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014 [ 151.764432] RIP: 0010:remove_and_add_spares.part.56+0x13c/0x3a0 [ 151.765061] RSP: 0018:ffffc90001d7fcd8 EFLAGS: 00010246 [ 151.765590] RAX: 0000000000000000 RBX: ffff88013601d600 RCX: 0000000000000000 [ 151.766306] RDX: 0000000000000000 RSI: ffff88013601d600 RDI: ffff880136187000 [ 151.767014] RBP: ffff880136187018 R08: 0000000000000003 R09: 0000000000000051 [ 151.767728] R10: ffffc90001d7fed8 R11: 0000000000000000 R12: ffff88013601d600 [ 151.768447] R13: ffff8801298b1300 R14: ffff880136187000 R15: 0000000000000000 [ 151.769160] FS: 00007f2624276700(0000) GS:ffff88013ae80000(0000) knlGS:0000000000000000 [ 151.769971] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 151.770554] CR2: 0000000000000060 CR3: 0000000111aac000 CR4: 00000000000006e0 [ 151.771272] Call Trace: [ 151.771542] md_ioctl+0x1df2/0x1e10 [ 151.771906] ? __switch_to+0x129/0x440 [ 151.772295] ? __schedule+0x244/0x850 [ 151.772672] blkdev_ioctl+0x4bd/0x970 [ 151.773048] block_ioctl+0x39/0x40 [ 151.773402] do_vfs_ioctl+0xa4/0x610 [ 151.773770] ? dput.part.23+0x87/0x100 [ 151.774151] ksys_ioctl+0x70/0x80 [ 151.774493] __x64_sys_ioctl+0x16/0x20 [ 151.774877] do_syscall_64+0x5b/0x180 [ 151.775258] entry_SYSCALL_64_after_hwframe+0x44/0xa9 For raid6, when two disk of the array are offline, two spare disks can be added into the array. Before spare disks recovery completing, system reboot and mdadm thinks it is ok to restart the degraded array by md_ioctl(). Since disks in raid6 is not only_parity(), raid5_run() will abort, when there is no PPL feature or not setting 'start_dirty_degraded' parameter. Therefore, mddev->pers is NULL. But, mddev->raid_disks has been set and it will not be cleared when raid5_run abort. md_ioctl() can execute cmd 'HOT_REMOVE_DISK' to remove a disk by mdadm, which will cause NULL pointer dereference in remove_and_add_spares() finally. Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx> --- drivers/md/md.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 3bea45e8ccff..817a6feb01e1 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6524,6 +6524,9 @@ static int hot_remove_disk(struct mddev *mddev, dev_t dev) char b[BDEVNAME_SIZE]; struct md_rdev *rdev; + if (!mddev->pers) + return -ENODEV; + rdev = find_rdev(mddev, dev); if (!rdev) return -ENXIO; -- 2.13.6 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
