LU-1540 e2fsck: add missing symlink NUL terminator

If a long symbolic link target is written into an external block
without a NUL terminator, its length is decided by the inode's size.
Make symlink check add a NUL termination in such cases if needed.

Such faulty symlinks were generated by osd-ldiskfs on the MDS until
Lustre 2.1.3 and Lustre 2.3.  The in-kernel code would handle such
unterminated symlinks correctly, since it used the inode size to
determine the symlink length, but e2fsck would assume the symlink
is broken if there wasn't a trailing NUL.

  LU-2627 e2fsck: check_symlink() SIGSEGV

  Since e2fsck_pass1_check_symlink() calls into check_symlink()
  with pctx == NULL, we should use 'ino' instead of 'pctx->ino'
  in check_symlink().

  Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
  Change-Id: If9c16f96d0655d5a886ef607f1f47ced6176f8d8

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I4419b30f1adb4a7d273796a936427aa351510213

diff --git a/e2fsck/e2fsck.h b/e2fsck/e2fsck.h
index a3e6c63..4aa76c3 100644 (file)
--- a/e2fsck/e2fsck.h
+++ b/e2fsck/e2fsck.h
@@ -517,7 +517,7 @@ extern void e2fsck_setup_tdb_icount(e2fsck_t ctx, int flags,
 extern void e2fsck_use_inode_shortcuts(e2fsck_t ctx, int use_shortcuts);
 extern int e2fsck_pass1_check_device_inode(ext2_filsys fs,
                                           struct ext2_inode *inode);
-extern int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
+extern int e2fsck_pass1_check_symlink(e2fsck_t ctx, ext2_ino_t ino,
                                      struct ext2_inode *inode, char *buf);
 extern void e2fsck_clear_inode(e2fsck_t ctx, ext2_ino_t ino,
                               struct ext2_inode *inode, int restart_flag,

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index 9bc35ee..9584a0c 100644 (file)
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -169,73 +169,96 @@ int e2fsck_pass1_check_device_inode(ext2_filsys fs EXT2FS_ATTR((unused)),
  * Check to make sure a symlink inode is real.  Returns 1 if the symlink
  * checks out, 0 if not.
  */
-int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
-                              struct ext2_inode *inode, char *buf)
+static int check_symlink(e2fsck_t ctx, struct problem_context *pctx,
+                        ext2_ino_t ino, struct ext2_inode *inode, char *buf)
 {
-       unsigned int len;
-       int i;
-       blk64_t blocks;
-       ext2_extent_handle_t    handle;
-       struct ext2_extent_info info;
-       struct ext2fs_extent    extent;
+       blk64_t block, num_blocks;
+       unsigned len, limit;
 
        if ((inode->i_size_high || inode->i_size == 0) ||
            (inode->i_flags & EXT2_INDEX_FL))
                return 0;
 
-       if (inode->i_flags & EXT4_EXTENTS_FL) {
-               if (inode->i_size > fs->blocksize)
+       num_blocks = ext2fs_inode_data_blocks2(ctx->fs, inode);
+       if (inode->i_flags & EXT4_EXTENTS_FL) { /* in extent-mapped block */
+               struct ext2_extent_info info;
+               ext2_extent_handle_t    handle;
+               struct ext2fs_extent    extent;
+
+               if (inode->i_size > ctx->fs->blocksize)
                        return 0;
-               if (ext2fs_extent_open2(fs, ino, inode, &handle))
+               if (ext2fs_extent_open2(ctx->fs, ino, inode, &handle))
                        return 0;
-               i = 0;
                if (ext2fs_extent_get_info(handle, &info) ||
                    (info.num_entries != 1) ||
-                   (info.max_depth != 0))
-                       goto exit_extent;
-               if (ext2fs_extent_get(handle, EXT2_EXTENT_ROOT, &extent) ||
+                   (info.max_depth != 0) ||
+
+                   ext2fs_extent_get(handle, EXT2_EXTENT_ROOT, &extent) ||
                    (extent.e_lblk != 0) ||
-                   (extent.e_len != 1) ||
-                   (extent.e_pblk < fs->super->s_first_data_block) ||
-                   (extent.e_pblk >= ext2fs_blocks_count(fs->super)))
-                       goto exit_extent;
-               i = 1;
-       exit_extent:
+                   (extent.e_len != 1)) {
+                       ext2fs_extent_free(handle);
+                       return 0;
+               }
+
+               block = extent.e_pblk;
+               limit = ctx->fs->blocksize;
+
                ext2fs_extent_free(handle);
-               return i;
-       }
+       } else if (num_blocks > 0) {            /* in block-mapped block */
+               int i;
 
-       blocks = ext2fs_inode_data_blocks2(fs, inode);
-       if (blocks) {
-               if ((inode->i_size >= fs->blocksize) ||
-                   (blocks != fs->blocksize >> 9) ||
-                   (inode->i_block[0] < fs->super->s_first_data_block) ||
-                   (inode->i_block[0] >= ext2fs_blocks_count(fs->super)))
-                       return 0;
+               block = inode->i_block[0];
+               limit = ctx->fs->blocksize;
 
                for (i = 1; i < EXT2_N_BLOCKS; i++)
                        if (inode->i_block[i])
                                return 0;
+       } else {                                /* inside inode i_block[] */
+               block = 0;
+               limit = sizeof(inode->i_block);
+       }
 
-               if (io_channel_read_blk64(fs->io, inode->i_block[0], 1, buf))
+       if (inode->i_size >= limit)
+               return 0;
+
+       if (num_blocks) {
+               if ((num_blocks != ctx->fs->blocksize >> 9) || /* == 1 block */
+                   (block < ctx->fs->super->s_first_data_block) ||
+                   (block >= ext2fs_blocks_count(ctx->fs->super)))
                        return 0;
 
-               len = strnlen(buf, fs->blocksize);
-               if (len == fs->blocksize)
+               if (io_channel_read_blk64(ctx->fs->io, block, 1, buf))
                        return 0;
        } else {
-               if (inode->i_size >= sizeof(inode->i_block))
-                       return 0;
+               buf = (char *)inode->i_block;
+       }
 
-               len = strnlen((char *)inode->i_block, sizeof(inode->i_block));
-               if (len == sizeof(inode->i_block))
-                       return 0;
+       len = strnlen(buf, limit);
+       /* Add missing NUL terminator at end of symlink (LU-1540),
+        * but only offer to fix this in pass1, not from pass2. */
+       if (len > inode->i_size && pctx != NULL &&
+           fix_problem(ctx, PR_1_SYMLINK_NUL, pctx)) {
+               buf[inode->i_size] = '\0';
+               if (num_blocks != 0) {
+                       if (io_channel_write_blk64(ctx->fs->io, block, 1, buf))
+                               return 0;
+               } else {
+                       e2fsck_write_inode(ctx, ino, inode, "check_ext_attr");
+               }
+               len = inode->i_size;
        }
        if (len != inode->i_size)
                return 0;
+
        return 1;
 }
 
+int e2fsck_pass1_check_symlink(e2fsck_t ctx, ext2_ino_t ino,
+                              struct ext2_inode *inode, char *buf)
+{
+       return check_symlink(ctx, NULL, ino, inode, buf);
+}
+
 /*
  * If the immutable (or append-only) flag is set on the inode, offer
  * to clear it.
@@ -1458,8 +1481,7 @@ void e2fsck_pass1(e2fsck_t ctx)
                        check_size(ctx, &pctx);
                        ctx->fs_blockdev_count++;
                } else if (LINUX_S_ISLNK (inode->i_mode) &&
-                          e2fsck_pass1_check_symlink(fs, ino, inode,
-                                                     block_buf)) {
+                          check_symlink(ctx, &pctx, ino, inode, block_buf)) {
                        check_immutable(ctx, &pctx);
                        ctx->fs_symlinks_count++;
                        if (ext2fs_inode_data_blocks(fs, inode) == 0) {

diff --git a/e2fsck/pass2.c b/e2fsck/pass2.c
index ff02f32..1aa6a3a 100644 (file)
--- a/e2fsck/pass2.c
+++ b/e2fsck/pass2.c
@@ -1404,8 +1404,8 @@ int e2fsck_process_bad_inode(e2fsck_t ctx, ext2_ino_t dir,
        else if (LINUX_S_ISSOCK(inode.i_mode)
                 && !e2fsck_pass1_check_device_inode(fs, &inode))
                problem = PR_2_BAD_SOCKET;
-       else if (LINUX_S_ISLNK(inode.i_mode)
-                && !e2fsck_pass1_check_symlink(fs, ino, &inode, buf)) {
+       else if (LINUX_S_ISLNK(inode.i_mode) &&
+                !e2fsck_pass1_check_symlink(ctx, ino, &inode, buf)) {
                problem = PR_2_INVALID_SYMLINK;
        }
 

diff --git a/e2fsck/problem.c b/e2fsck/problem.c
index a56c126..26bbf80 100644 (file)
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -999,6 +999,11 @@ static struct e2fsck_problem problem_table[] = {
          N_("@a in @i %i is corrupt (@n value)."),
          PROMPT_CLEAR, 0},
 
+       /* Bad extended attribute value in inode */
+       { PR_1_SYMLINK_NUL,
+         N_("@i %i symlink missing NUL terminator.  "),
+         PROMPT_FIX, 0},
+
        /* expand inode */
        { PR_1_EXPAND_EISIZE_WARNING,
          N_("\ne2fsck is being run with \"expand_extra_isize\" option or\n"

diff --git a/e2fsck/problem.h b/e2fsck/problem.h
index c1afb84..e96b115 100644 (file)
--- a/e2fsck/problem.h
+++ b/e2fsck/problem.h
@@ -599,6 +599,9 @@ struct problem_context {
 /* Bad extended attribute value in inode */
 #define PR_1_INODE_EA_BAD_VALUE                0x010080
 
+/* Symlink missing NUL terminator */
+#define PR_1_SYMLINK_NUL               0x010081
+
 /* Warning for user that all inodes need to be expanded atleast by
  * s_min_extra_isize
  */

diff --git a/tests/f_badsymlinks/expect.1 b/tests/f_badsymlinks/expect.1
index b28b57d..f300fca 100644 (file)
--- a/tests/f_badsymlinks/expect.1
+++ b/tests/f_badsymlinks/expect.1
@@ -1,4 +1,8 @@
 Pass 1: Checking inodes, blocks, and sizes
+Inode 13 symlink missing NUL terminator.  Fix? yes
+
+Inode 14 symlink missing NUL terminator.  Fix? yes
+
 Special (device/socket/fifo/symlink) file (inode 18) has immutable
 or append-only flag set.  Clear? yes
 
@@ -19,12 +23,6 @@ Pass 2: Checking directory structure
 Symlink /empty_link (inode #17) is invalid.
 Clear? yes
 
-Symlink /long_fastlink (inode #13) is invalid.
-Clear? yes
-
-Symlink /long_link (inode #14) is invalid.
-Clear? yes
-
 Symlink /high_fastlink (inode #15) is invalid.
 Clear? yes
 
@@ -49,13 +47,13 @@ Clear? yes
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
-Free blocks count wrong for group #0 (1000, counted=1001).
+Free blocks count wrong for group #0 (999, counted=1000).
 Fix? yes
 
-Free blocks count wrong (1000, counted=1001).
+Free blocks count wrong (999, counted=1000).
 Fix? yes
 
 
 test_filesys: ***** FILE SYSTEM WAS MODIFIED *****
-test_filesys: 13/32 files (7.7% non-contiguous), 23/1024 blocks
+test_filesys: 15/32 files (6.7% non-contiguous), 24/1024 blocks
 Exit status is 1

diff --git a/tests/f_badsymlinks/expect.2 b/tests/f_badsymlinks/expect.2
index 1499551..f361d8d 100644 (file)
--- a/tests/f_badsymlinks/expect.2
+++ b/tests/f_badsymlinks/expect.2
@@ -3,5 +3,5 @@ Pass 2: Checking directory structure
 Pass 3: Checking directory connectivity
 Pass 4: Checking reference counts
 Pass 5: Checking group summary information
-test_filesys: 13/32 files (0.0% non-contiguous), 23/1024 blocks
+test_filesys: 15/32 files (0.0% non-contiguous), 24/1024 blocks
 Exit status is 0