ntfs: do not dereference a null ctx on error

In ntfs_mft_data_extend_allocation_nolock(), if an error condition occurs
prior to 'ctx' being set to a non-NULL value, avoid dereferencing the NULL
'ctx' pointer in error handling.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Danila Chernetsov <listdansp@mail.ru>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
index 48030899dc6ec34a6741967d20fa8e3f66a5500d..0155f106ec344a3486c52c2c420478619c972931 100644 (file)
--- a/fs/ntfs/mft.c
+++ b/fs/ntfs/mft.c
@@ -1955,36 +1955,38 @@ undo_alloc:
                                "attribute.%s", es);
                NVolSetErrors(vol);
        }
-       a = ctx->attr;
+
        if (ntfs_rl_truncate_nolock(vol, &mft_ni->runlist, old_last_vcn)) {
                ntfs_error(vol->sb, "Failed to truncate mft data attribute "
                                "runlist.%s", es);
                NVolSetErrors(vol);
        }
-       if (mp_rebuilt && !IS_ERR(ctx->mrec)) {
-               if (ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
+       if (ctx) {
+               a = ctx->attr;
+               if (mp_rebuilt && !IS_ERR(ctx->mrec)) {
+                       if (ntfs_mapping_pairs_build(vol, (u8 *)a + le16_to_cpu(
                                a->data.non_resident.mapping_pairs_offset),
                                old_alen - le16_to_cpu(
-                               a->data.non_resident.mapping_pairs_offset),
+                                       a->data.non_resident.mapping_pairs_offset),
                                rl2, ll, -1, NULL)) {
-                       ntfs_error(vol->sb, "Failed to restore mapping pairs "
+                               ntfs_error(vol->sb, "Failed to restore mapping pairs "
                                        "array.%s", es);
-                       NVolSetErrors(vol);
-               }
-               if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
-                       ntfs_error(vol->sb, "Failed to restore attribute "
+                               NVolSetErrors(vol);
+                       }
+                       if (ntfs_attr_record_resize(ctx->mrec, a, old_alen)) {
+                               ntfs_error(vol->sb, "Failed to restore attribute "
                                        "record.%s", es);
+                               NVolSetErrors(vol);
+                       }
+                       flush_dcache_mft_record_page(ctx->ntfs_ino);
+                       mark_mft_record_dirty(ctx->ntfs_ino);
+               } else if (IS_ERR(ctx->mrec)) {
+                       ntfs_error(vol->sb, "Failed to restore attribute search "
+                               "context.%s", es);
                        NVolSetErrors(vol);
                }
-               flush_dcache_mft_record_page(ctx->ntfs_ino);
-               mark_mft_record_dirty(ctx->ntfs_ino);
-       } else if (IS_ERR(ctx->mrec)) {
-               ntfs_error(vol->sb, "Failed to restore attribute search "
-                               "context.%s", es);
-               NVolSetErrors(vol);
-       }
-       if (ctx)
                ntfs_attr_put_search_ctx(ctx);
+       }
        if (!IS_ERR(mrec))
                unmap_mft_record(mft_ni);
        up_write(&mft_ni->runlist.lock);