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dm btree remove: assign new_root only when removal succeeds

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remove_raw() in dm_btree_remove() may fail due to IO read error
(e.g. read the content of origin block fails during shadowing),
and the value of shadow_spine::root is uninitialized, but
the uninitialized value is still assign to new_root in the
end of dm_btree_remove().

For dm-thin, the value of pmd->details_root or pmd->root will become
an uninitialized value, so if trying to read details_info tree again
out-of-bound memory may occur as showed below:

  general protection fault, probably for non-canonical address 0x3fdcb14c8d7520
  CPU: 4 PID: 515 Comm: dmsetup Not tainted 5.13.0-rc6
  Hardware name: QEMU Standard PC
  RIP: 0010:metadata_ll_load_ie+0x14/0x30
  Call Trace:
   sm_metadata_count_is_more_than_one+0xb9/0xe0
   dm_tm_shadow_block+0x52/0x1c0
   shadow_step+0x59/0xf0
   remove_raw+0xb2/0x170
   dm_btree_remove+0xf4/0x1c0
   dm_pool_delete_thin_device+0xc3/0x140
   pool_message+0x218/0x2b0
   target_message+0x251/0x290
   ctl_ioctl+0x1c4/0x4d0
   dm_ctl_ioctl+0xe/0x20
   __x64_sys_ioctl+0x7b/0xb0
   do_syscall_64+0x40/0xb0
   entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixing it by only assign new_root when removal succeeds

Signed-off-by: Hou Tao <houtao1@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Hou Tao 2021-06-17 15:45:47 +08:00 committed by Mike Snitzer
parent 28436ba34b
commit b6e58b5466
1 changed files with 2 additions and 1 deletions
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3
drivers/md/persistent-data/dm-btree-remove.c
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@ -549,7 +549,8 @@ int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
delete_at(n, index);
}
*new_root = shadow_root(&spine);
if (!r)
*new_root = shadow_root(&spine);
exit_shadow_spine(&spine);
return r;