6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dongjiang Zhu [ Upstream commit 51a0e8399858621442807a26057bcd1cd3ced046 ] [BUG] Mounting with rescue=ibadroots after corrupting the block group tree root triggers a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000100 RIP: 0010:btrfs_update_global_block_rsv+0x9d/0x1c0 [btrfs] Call Trace: fill_dummy_bgs+0xd4/0x120 [btrfs] open_ctree+0xc6e/0x1ca0 [btrfs] btrfs_get_tree+0x50d/0xa40 [btrfs] The same crash occurs with a corrupted raid stripe tree root, via btrfs_read_block_groups() instead of fill_dummy_bgs(). [CAUSE] With rescue=ibadroots, btrfs_read_roots() allows the mount to continue when either root cannot be read, leaving the corresponding root pointer NULL while its on-disk feature bit remains set. btrfs_update_global_block_rsv() then dereferences the missing root based on the feature bit alone. [FIX] Rescue mounts are fully read-only and cannot start transactions, so the global reserve is never consumed. Under btrfs_is_full_ro(), mark the reserve as full and return before performing the accounting. And since we need to check if the fs is mount fully RO, export fs_is_full_ro() as btrfs_is_full_ro(), and move it to fs.h. Fixes: 8dbfc14fc736 ("btrfs: account block group tree when calculating global reserve size") Fixes: 515020900d44 ("btrfs: read raid stripe tree from disk") Suggested-by: Qu Wenruo Signed-off-by: Dongjiang Zhu [ Squash the fs_is_full_ro() export commit into this one. ] Reviewed-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/block-rsv.c | 19 +++++++++++++++++-- fs/btrfs/disk-io.c | 11 +---------- fs/btrfs/fs.h | 9 +++++++++ 3 files changed, 27 insertions(+), 12 deletions(-) diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c index 07bf07431a7f4..14530d436d6ef 100644 --- a/fs/btrfs/block-rsv.c +++ b/fs/btrfs/block-rsv.c @@ -324,10 +324,25 @@ void btrfs_block_rsv_add_bytes(struct btrfs_block_rsv *block_rsv, void btrfs_update_global_block_rsv(struct btrfs_fs_info *fs_info) { struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv; - struct btrfs_space_info *sinfo = block_rsv->space_info; + struct btrfs_space_info *sinfo; struct btrfs_root *root, *tmp; - u64 num_bytes = btrfs_root_used(&fs_info->tree_root->root_item); unsigned int min_items = 1; + u64 num_bytes; + + /* + * A full read-only mount (rescue options) cannot start transactions, + * so the global reserve is never consumed. Mark it as full and skip + * the accounting. + */ + if (btrfs_is_full_ro(fs_info)) { + spin_lock(&block_rsv->lock); + block_rsv->full = true; + spin_unlock(&block_rsv->lock); + return; + } + + sinfo = block_rsv->space_info; + num_bytes = btrfs_root_used(&fs_info->tree_root->root_item); /* * The global block rsv is based on the size of the extent tree, the diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index e025399abce97..20253e3e5f820 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -3155,15 +3155,6 @@ int btrfs_check_features(struct btrfs_fs_info *fs_info, bool is_rw_mount) return 0; } -static bool fs_is_full_ro(const struct btrfs_fs_info *fs_info) -{ - if (!sb_rdonly(fs_info->sb)) - return false; - if (unlikely(fs_info->mount_opt & BTRFS_MOUNT_FULL_RO_MASK)) - return true; - return false; -} - int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_devices, char *options) { @@ -3308,7 +3299,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device goto fail_alloc; /* If the fs has any rescue options, no transaction is allowed. */ - if (fs_is_full_ro(fs_info)) + if (btrfs_is_full_ro(fs_info)) WRITE_ONCE(fs_info->fs_error, -EROFS); ret = btrfs_check_features(fs_info, !sb_rdonly(sb)); diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h index 415f867dd1252..88c779635483f 100644 --- a/fs/btrfs/fs.h +++ b/fs/btrfs/fs.h @@ -948,6 +948,15 @@ do { \ btrfs_clear_opt(fs_info->mount_opt, opt); \ } while (0) +static inline bool btrfs_is_full_ro(const struct btrfs_fs_info *fs_info) +{ + if (!sb_rdonly(fs_info->sb)) + return false; + if (unlikely(fs_info->mount_opt & BTRFS_MOUNT_FULL_RO_MASK)) + return true; + return false; +} + static inline int btrfs_fs_closing(struct btrfs_fs_info *fs_info) { /* Do it this way so we only ever do one test_bit in the normal case. */ -- 2.53.0