e2fsck: Go back to the original superblock if the backup sb is invalid

In the case where the block group descriptors appear corrupt, e2fsck
will try to use the backup superblock.  However, it could be that the
backup superblock itself is completely corrupted, in which e2fsck
should go back to the original superblock instead of refusing to fix
the file system.

Addresses-Debian-Bug: #516820

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/e2fsck/unix.c b/e2fsck/unix.c
index 3e684ae..ffcdcc6 100644 (file)
--- a/e2fsck/unix.c
+++ b/e2fsck/unix.c
@@ -890,6 +890,38 @@ sscanf_err:
        exit (1);
 }
 
+static errcode_t try_open_fs(e2fsck_t ctx, int flags, io_manager io_ptr,
+                            ext2_filsys *ret_fs)
+{
+       errcode_t retval;
+
+       *ret_fs = NULL;
+       if (ctx->superblock && ctx->blocksize) {
+               retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
+                                     flags, ctx->superblock, ctx->blocksize,
+                                     io_ptr, ret_fs);
+       } else if (ctx->superblock) {
+               int blocksize;
+               for (blocksize = EXT2_MIN_BLOCK_SIZE;
+                    blocksize <= EXT2_MAX_BLOCK_SIZE; blocksize *= 2) {
+                       if (*ret_fs) {
+                               ext2fs_free(*ret_fs);
+                               *ret_fs = NULL;
+                       }
+                       retval = ext2fs_open2(ctx->filesystem_name,
+                                             ctx->io_options, flags,
+                                             ctx->superblock, blocksize,
+                                             io_ptr, ret_fs);
+                       if (!retval)
+                               break;
+               }
+       } else
+               retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
+                                     flags, 0, 0, io_ptr, ret_fs);
+       return retval;
+}
+
+
 static const char *my_ver_string = E2FSPROGS_VERSION;
 static const char *my_ver_date = E2FSPROGS_DATE;
 
@@ -903,6 +935,7 @@ int main (int argc, char *argv[])
        const char      *lib_ver_date;
        int             my_ver, lib_ver;
        e2fsck_t        ctx;
+       blk_t           orig_superblock;
        struct problem_context pctx;
        int flags, run_result;
        int journal_size;
@@ -974,26 +1007,8 @@ restart:
        if ((ctx->mount_flags & EXT2_MF_MOUNTED) == 0)
                flags |= EXT2_FLAG_EXCLUSIVE;
 
-       if (ctx->superblock && ctx->blocksize) {
-               retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
-                                     flags, ctx->superblock, ctx->blocksize,
-                                     io_ptr, &fs);
-       } else if (ctx->superblock) {
-               int blocksize;
-               for (blocksize = EXT2_MIN_BLOCK_SIZE;
-                    blocksize <= EXT2_MAX_BLOCK_SIZE; blocksize *= 2) {
-                       if (fs)
-                               ext2fs_free(fs);
-                       retval = ext2fs_open2(ctx->filesystem_name,
-                                             ctx->io_options, flags,
-                                             ctx->superblock, blocksize,
-                                             io_ptr, &fs);
-                       if (!retval)
-                               break;
-               }
-       } else
-               retval = ext2fs_open2(ctx->filesystem_name, ctx->io_options,
-                                     flags, 0, 0, io_ptr, &fs);
+       retval = try_open_fs(ctx, flags, io_ptr, &fs);
+
        if (!ctx->superblock && !(ctx->options & E2F_OPT_PREEN) &&
            !(ctx->flags & E2F_FLAG_SB_SPECIFIED) &&
            ((retval == EXT2_ET_BAD_MAGIC) ||
@@ -1008,11 +1023,20 @@ restart:
                               ctx->program_name,
                               retval ? _("Superblock invalid,") :
                               _("Group descriptors look bad..."));
+                       orig_superblock = ctx->superblock;
                        get_backup_sb(ctx, fs, ctx->filesystem_name, io_ptr);
                        if (fs)
                                ext2fs_close(fs);
                        orig_retval = retval;
-                       goto restart;
+                       retval = try_open_fs(ctx, flags, io_ptr, &fs);
+                       if ((orig_retval == 0) && retval != 0) {
+                               com_err(ctx->program_name, retval,
+                                       "when using the backup blocks");
+                               printf(_("%s: going back to original "
+                                        "superblock\n"), ctx->program_name);
+                               ctx->superblock = orig_superblock;
+                               retval = try_open_fs(ctx, flags, io_ptr, &fs);
+                       }
                }
        }
        if (((retval == EXT2_ET_UNSUPP_FEATURE) ||