From 59f37036bb7ab3d554c24abc856aabca01126414 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Sat, 15 Feb 2025 11:36:15 +0000 Subject: [PATCH] btrfs: fix use-after-free on inode when scanning root during em shrinking At btrfs_scan_root() we are accessing the inode's root (and fs_info) in a call to btrfs_fs_closing() after we have scheduled the inode for a delayed iput, and that can result in a use-after-free on the inode in case the cleaner kthread does the iput before we dereference the inode in the call to btrfs_fs_closing(). Fix this by using the fs_info stored already in a local variable instead of doing inode->root->fs_info. Fixes: 102044384056 ("btrfs: make the extent map shrinker run asynchronously as a work queue job") CC: stable@vger.kernel.org # 6.13+ Tested-by: Ivan Shapovalov Link: https://lore.kernel.org/linux-btrfs/0414d690ac5680d0d77dfc930606cdc36e42e12f.camel@intelfx.name/ Reviewed-by: Johannes Thumshirn Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/extent_map.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 67ce85ff0ae2..bee1b94a1049 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -1222,8 +1222,7 @@ static long btrfs_scan_root(struct btrfs_root *root, struct btrfs_em_shrink_ctx fs_info->em_shrinker_last_ino = btrfs_ino(inode); btrfs_add_delayed_iput(inode); - if (ctx->scanned >= ctx->nr_to_scan || - btrfs_fs_closing(inode->root->fs_info)) + if (ctx->scanned >= ctx->nr_to_scan || btrfs_fs_closing(fs_info)) break; cond_resched();