[PATCH] Test for sb_getblk return value

This patch adds tests for the return value of sb_getblk() in the ext2/3
filesystems.  In fs/buffer.c it is stated that the getblk() function never
fails.  However, it does can return NULL in some situations due to I/O
errors, which may lead us to NULL pointer dereferences

Signed-off-by: Glauber de Oliveira Costa <glommer@br.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/ext3/resize.c b/fs/ext3/resize.c
index 57f79106267d..1be78b4b4de9 100644
--- a/fs/ext3/resize.c
+++ b/fs/ext3/resize.c
@@ -118,6 +118,8 @@ static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
         int err;
 
         bh = sb_getblk(sb, blk);
+        if (!bh)
+                return ERR_PTR(-EIO);
         if ((err = ext3_journal_get_write_access(handle, bh))) {
                 brelse(bh);
                 bh = ERR_PTR(err);
@@ -202,6 +204,10 @@ static int setup_new_group_blocks(struct super_block *sb,
                 ext3_debug("update backup group %#04lx (+%d)\n", block, bit);
 
                 gdb = sb_getblk(sb, block);
+                if (!gdb) {
+                        err = -EIO;
+                        goto exit_bh;
+                }
                 if ((err = ext3_journal_get_write_access(handle, gdb))) {
                         brelse(gdb);
                         goto exit_bh;
@@ -643,6 +649,10 @@ static void update_backups(struct super_block *sb,
                         break;
 
                 bh = sb_getblk(sb, group * bpg + blk_off);
+                if (!bh) {
+                        err = -EIO;
+                        break;
+                }
                 ext3_debug("update metadata backup %#04lx\n",
                           (unsigned long)bh->b_blocknr);
                 if ((err = ext3_journal_get_write_access(handle, bh)))