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f2fs: fix UAF in f2fs_available_free_memory 

if2fs_fill_super
-> f2fs_build_segment_manager
   -> create_discard_cmd_control
      -> f2fs_start_discard_thread

It invokes kthread_run to create a thread and run issue_discard_thread.

However, if f2fs_build_node_manager fails, the control flow goes to
free_nm and calls f2fs_destroy_node_manager. This function will free
sbi->nm_info. However, if issue_discard_thread accesses sbi->nm_info
after the deallocation, but before the f2fs_stop_discard_thread, it will
cause UAF(Use-after-free).

-> f2fs_destroy_segment_manager
   -> destroy_discard_cmd_control
      -> f2fs_stop_discard_thread

Fix this by stopping discard thread before f2fs_destroy_node_manager.

Note that, the commit d6d2b491a8 introduces the call of
f2fs_available_free_memory into issue_discard_thread.

Cc: stable@vger.kernel.org
Fixes: d6d2b491a8 ("f2fs: allow to change discard policy based on cached discard cmds")
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Dongliang Mu 2021-11-04 16:22:01 +08:00 committed by Jaegeuk Kim
parent e3b49ea368
commit 5429c9dbc9
1 changed files with 2 additions and 0 deletions
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2
fs/f2fs/super.c
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@ -4385,6 +4385,8 @@ free_node_inode:
free_stats:
f2fs_destroy_stats(sbi);
free_nm:
/* stop discard thread before destroying node manager */
f2fs_stop_discard_thread(sbi);
f2fs_destroy_node_manager(sbi);
free_sm:
f2fs_destroy_segment_manager(sbi);