4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: DingXiang <dingxiang@xxxxxxxxxx> commit 4df2bf466a9c9c92f40d27c4aa9120f4e8227bfc upstream. Otherwise loading a "snapshot" table using the same device for the origin and COW devices, e.g.: echo "0 20971520 snapshot 253:3 253:3 P 8" | dmsetup create snap will trigger: BUG: unable to handle kernel NULL pointer dereference at 0000000000000098 [ 1958.979934] IP: [<ffffffffa040efba>] dm_exception_store_set_chunk_size+0x7a/0x110 [dm_snapshot] [ 1958.989655] PGD 0 [ 1958.991903] Oops: 0000 [#1] SMP ... [ 1959.059647] CPU: 9 PID: 3556 Comm: dmsetup Tainted: G IO 4.5.0-rc5.snitm+ #150 ... [ 1959.083517] task: ffff8800b9660c80 ti: ffff88032a954000 task.ti: ffff88032a954000 [ 1959.091865] RIP: 0010:[<ffffffffa040efba>] [<ffffffffa040efba>] dm_exception_store_set_chunk_size+0x7a/0x110 [dm_snapshot] [ 1959.104295] RSP: 0018:ffff88032a957b30 EFLAGS: 00010246 [ 1959.110219] RAX: 0000000000000000 RBX: 0000000000000008 RCX: 0000000000000001 [ 1959.118180] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff880329334a00 [ 1959.126141] RBP: ffff88032a957b50 R08: 0000000000000000 R09: 0000000000000001 [ 1959.134102] R10: 000000000000000a R11: f000000000000000 R12: ffff880330884d80 [ 1959.142061] R13: 0000000000000008 R14: ffffc90001c13088 R15: ffff880330884d80 [ 1959.150021] FS: 00007f8926ba3840(0000) GS:ffff880333440000(0000) knlGS:0000000000000000 [ 1959.159047] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1959.165456] CR2: 0000000000000098 CR3: 000000032f48b000 CR4: 00000000000006e0 [ 1959.173415] Stack: [ 1959.175656] ffffc90001c13040 ffff880329334a00 ffff880330884ed0 ffff88032a957bdc [ 1959.183946] ffff88032a957bb8 ffffffffa040f225 ffff880329334a30 ffff880300000000 [ 1959.192233] ffffffffa04133e0 ffff880329334b30 0000000830884d58 00000000569c58cf [ 1959.200521] Call Trace: [ 1959.203248] [<ffffffffa040f225>] dm_exception_store_create+0x1d5/0x240 [dm_snapshot] [ 1959.211986] [<ffffffffa040d310>] snapshot_ctr+0x140/0x630 [dm_snapshot] [ 1959.219469] [<ffffffffa0005c44>] ? dm_split_args+0x64/0x150 [dm_mod] [ 1959.226656] [<ffffffffa0005ea7>] dm_table_add_target+0x177/0x440 [dm_mod] [ 1959.234328] [<ffffffffa0009203>] table_load+0x143/0x370 [dm_mod] [ 1959.241129] [<ffffffffa00090c0>] ? retrieve_status+0x1b0/0x1b0 [dm_mod] [ 1959.248607] [<ffffffffa0009e35>] ctl_ioctl+0x255/0x4d0 [dm_mod] [ 1959.255307] [<ffffffff813304e2>] ? memzero_explicit+0x12/0x20 [ 1959.261816] [<ffffffffa000a0c3>] dm_ctl_ioctl+0x13/0x20 [dm_mod] [ 1959.268615] [<ffffffff81215eb6>] do_vfs_ioctl+0xa6/0x5c0 [ 1959.274637] [<ffffffff81120d2f>] ? __audit_syscall_entry+0xaf/0x100 [ 1959.281726] [<ffffffff81003176>] ? do_audit_syscall_entry+0x66/0x70 [ 1959.288814] [<ffffffff81216449>] SyS_ioctl+0x79/0x90 [ 1959.294450] [<ffffffff8167e4ae>] entry_SYSCALL_64_fastpath+0x12/0x71 ... [ 1959.323277] RIP [<ffffffffa040efba>] dm_exception_store_set_chunk_size+0x7a/0x110 [dm_snapshot] [ 1959.333090] RSP <ffff88032a957b30> [ 1959.336978] CR2: 0000000000000098 [ 1959.344121] ---[ end trace b049991ccad1169e ]--- Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1195899 Signed-off-by: Ding Xiang <dingxiang@xxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/dm-snap.c | 9 +++++++++ drivers/md/dm-table.c | 36 ++++++++++++++++++++++++------------ include/linux/device-mapper.h | 2 ++ 3 files changed, 35 insertions(+), 12 deletions(-) --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1106,6 +1106,7 @@ static int snapshot_ctr(struct dm_target int i; int r = -EINVAL; char *origin_path, *cow_path; + dev_t origin_dev, cow_dev; unsigned args_used, num_flush_bios = 1; fmode_t origin_mode = FMODE_READ; @@ -1136,11 +1137,19 @@ static int snapshot_ctr(struct dm_target ti->error = "Cannot get origin device"; goto bad_origin; } + origin_dev = s->origin->bdev->bd_dev; cow_path = argv[0]; argv++; argc--; + cow_dev = dm_get_dev_t(cow_path); + if (cow_dev && cow_dev == origin_dev) { + ti->error = "COW device cannot be the same as origin device"; + r = -EINVAL; + goto bad_cow; + } + r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow); if (r) { ti->error = "Cannot get COW device"; --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -365,6 +365,26 @@ static int upgrade_mode(struct dm_dev_in } /* + * Convert the path to a device + */ +dev_t dm_get_dev_t(const char *path) +{ + dev_t uninitialized_var(dev); + struct block_device *bdev; + + bdev = lookup_bdev(path); + if (IS_ERR(bdev)) + dev = name_to_dev_t(path); + else { + dev = bdev->bd_dev; + bdput(bdev); + } + + return dev; +} +EXPORT_SYMBOL_GPL(dm_get_dev_t); + +/* * Add a device to the list, or just increment the usage count if * it's already present. */ @@ -372,23 +392,15 @@ int dm_get_device(struct dm_target *ti, struct dm_dev **result) { int r; - dev_t uninitialized_var(dev); + dev_t dev; struct dm_dev_internal *dd; struct dm_table *t = ti->table; - struct block_device *bdev; BUG_ON(!t); - /* convert the path to a device */ - bdev = lookup_bdev(path); - if (IS_ERR(bdev)) { - dev = name_to_dev_t(path); - if (!dev) - return -ENODEV; - } else { - dev = bdev->bd_dev; - bdput(bdev); - } + dev = dm_get_dev_t(path); + if (!dev) + return -ENODEV; dd = find_device(&t->devices, dev); if (!dd) { --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -124,6 +124,8 @@ struct dm_dev { char name[16]; }; +dev_t dm_get_dev_t(const char *path); + /* * Constructors should call these functions to ensure destination devices * are opened/closed correctly. -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html