From: Sasha Levin Date: Wed, 2 Jul 2025 23:02:58 +0000 (-0400) Subject: btrfs: fix use-after-free on inode when scanning root during em shrinking X-Git-Tag: v6.12.36~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=07836bc18f4ae42da4e922244f4685561c18755e;p=thirdparty%2Fkernel%2Fstable.git btrfs: fix use-after-free on inode when scanning root during em shrinking [ Upstream commit 59f37036bb7ab3d554c24abc856aabca01126414 ] 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 Signed-off-by: Sasha Levin --- diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 93043edc8ff93..36af9aa9aab13 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -1250,6 +1250,7 @@ next: static long btrfs_scan_root(struct btrfs_root *root, struct btrfs_em_shrink_ctx *ctx) { + struct btrfs_fs_info *fs_info = root->fs_info; struct btrfs_inode *inode; long nr_dropped = 0; u64 min_ino = ctx->last_ino + 1; @@ -1264,7 +1265,7 @@ static long btrfs_scan_root(struct btrfs_root *root, struct btrfs_em_shrink_ctx iput(&inode->vfs_inode); if (ctx->scanned >= ctx->nr_to_scan || - btrfs_fs_closing(inode->root->fs_info)) + btrfs_fs_closing(fs_info)) break; cond_resched();