ext4: lock the xattr block before checksuming it

We must lock the xattr block before calculating or verifying the
checksum in order to avoid spurious checksum failures.

https://bugzilla.kernel.org/show_bug.cgi?id=193661

Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

1 files changed, 31 insertions, 34 deletions

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 67636acf7624..996e7900d4c8 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -131,31 +131,26 @@ static __le32 ext4_xattr_block_csum(struct inode *inode,
 }
 
 static int ext4_xattr_block_csum_verify(struct inode *inode,
-                                        sector_t block_nr,
-                                        struct ext4_xattr_header *hdr)
+                                        struct buffer_head *bh)
 {
-        if (ext4_has_metadata_csum(inode->i_sb) &&
-            (hdr->h_checksum != ext4_xattr_block_csum(inode, block_nr, hdr)))
-                return 0;
-        return 1;
-}
-
-static void ext4_xattr_block_csum_set(struct inode *inode,
-                                      sector_t block_nr,
-                                      struct ext4_xattr_header *hdr)
-{
-        if (!ext4_has_metadata_csum(inode->i_sb))
-                return;
+        struct ext4_xattr_header *hdr = BHDR(bh);
+        int ret = 1;
 
-        hdr->h_checksum = ext4_xattr_block_csum(inode, block_nr, hdr);
+        if (ext4_has_metadata_csum(inode->i_sb)) {
+                lock_buffer(bh);
+                ret = (hdr->h_checksum == ext4_xattr_block_csum(inode,
+                                                        bh->b_blocknr, hdr));
+                unlock_buffer(bh);
+        }
+        return ret;
 }
 
-static inline int ext4_handle_dirty_xattr_block(handle_t *handle,
-                                                struct inode *inode,
-                                                struct buffer_head *bh)
+static void ext4_xattr_block_csum_set(struct inode *inode,
+                                      struct buffer_head *bh)
 {
-        ext4_xattr_block_csum_set(inode, bh->b_blocknr, BHDR(bh));
-        return ext4_handle_dirty_metadata(handle, inode, bh);
+        if (ext4_has_metadata_csum(inode->i_sb))
+                BHDR(bh)->h_checksum = ext4_xattr_block_csum(inode,
+                                                bh->b_blocknr, BHDR(bh));
 }
 
 static inline const struct xattr_handler *
@@ -233,7 +228,7 @@ ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh)
         if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
             BHDR(bh)->h_blocks != cpu_to_le32(1))
                 return -EFSCORRUPTED;
-        if (!ext4_xattr_block_csum_verify(inode, bh->b_blocknr, BHDR(bh)))
+        if (!ext4_xattr_block_csum_verify(inode, bh))
                 return -EFSBADCRC;
         error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size,
                                        bh->b_data);
@@ -618,23 +613,22 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
                         }
                 }
 
+                ext4_xattr_block_csum_set(inode, bh);
                 /*
                  * Beware of this ugliness: Releasing of xattr block references
                  * from different inodes can race and so we have to protect
                  * from a race where someone else frees the block (and releases
                  * its journal_head) before we are done dirtying the buffer. In
                  * nojournal mode this race is harmless and we actually cannot
-                 * call ext4_handle_dirty_xattr_block() with locked buffer as
+                 * call ext4_handle_dirty_metadata() with locked buffer as
                  * that function can call sync_dirty_buffer() so for that case
                  * we handle the dirtying after unlocking the buffer.
                  */
                 if (ext4_handle_valid(handle))
-                        error = ext4_handle_dirty_xattr_block(handle, inode,
-                                                              bh);
+                        error = ext4_handle_dirty_metadata(handle, inode, bh);
                 unlock_buffer(bh);
                 if (!ext4_handle_valid(handle))
-                        error = ext4_handle_dirty_xattr_block(handle, inode,
-                                                              bh);
+                        error = ext4_handle_dirty_metadata(handle, inode, bh);
                 if (IS_SYNC(inode))
                         ext4_handle_sync(handle);
                 dquot_free_block(inode, EXT4_C2B(EXT4_SB(inode->i_sb), 1));
@@ -863,13 +857,14 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
                                 ext4_xattr_cache_insert(ext4_mb_cache,
                                         bs->bh);
                         }
+                        ext4_xattr_block_csum_set(inode, bs->bh);
                         unlock_buffer(bs->bh);
                         if (error == -EFSCORRUPTED)
                                 goto bad_block;
                         if (!error)
-                                error = ext4_handle_dirty_xattr_block(handle,
-                                                                      inode,
-                                                                      bs->bh);
+                                error = ext4_handle_dirty_metadata(handle,
+                                                                   inode,
+                                                                   bs->bh);
                         if (error)
                                 goto cleanup;
                         goto inserted;
@@ -967,10 +962,11 @@ inserted:
                                         ce->e_reusable = 0;
                                 ea_bdebug(new_bh, "reusing; refcount now=%d",
                                           ref);
+                                ext4_xattr_block_csum_set(inode, new_bh);
                                 unlock_buffer(new_bh);
-                                error = ext4_handle_dirty_xattr_block(handle,
-                                                                      inode,
-                                                                      new_bh);
+                                error = ext4_handle_dirty_metadata(handle,
+                                                                   inode,
+                                                                   new_bh);
                                 if (error)
                                         goto cleanup_dquot;
                         }
@@ -1020,11 +1016,12 @@ getblk_failed:
                                 goto getblk_failed;
                         }
                         memcpy(new_bh->b_data, s->base, new_bh->b_size);
+                        ext4_xattr_block_csum_set(inode, new_bh);
                         set_buffer_uptodate(new_bh);
                         unlock_buffer(new_bh);
                         ext4_xattr_cache_insert(ext4_mb_cache, new_bh);
-                        error = ext4_handle_dirty_xattr_block(handle,
-                                                              inode, new_bh);
+                        error = ext4_handle_dirty_metadata(handle, inode,
+                                                           new_bh);
                         if (error)
                                 goto cleanup;
                 }