[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>

3 files changed, 22 insertions, 1 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index fdba4d1d3c60..e7d3f0522d01 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -440,6 +440,10 @@ static int ext2_alloc_branch(struct inode *inode,
                  * the pointer to new one, then send parent to disk.
                  */
                 bh = sb_getblk(inode->i_sb, parent);
+                if (!bh) {
+                        err = -EIO;
+                        break;
+                }
                 lock_buffer(bh);
                 memset(bh->b_data, 0, blocksize);
                 branch[n].bh = bh;
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index b5da5244e144..5d9b00e28837 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -523,7 +523,6 @@ static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
                         if (!nr)
                                 break;
                         branch[n].key = cpu_to_le32(nr);
-                        keys = n+1;
 
                         /*
                          * Get buffer_head for parent block, zero it out
@@ -531,6 +530,9 @@ static int ext3_alloc_branch(handle_t *handle, struct inode *inode,
                          * parent to disk.  
                          */
                         bh = sb_getblk(inode->i_sb, parent);
+                        if (!bh)
+                                break;
+                        keys = n+1;
                         branch[n].bh = bh;
                         lock_buffer(bh);
                         BUFFER_TRACE(bh, "call get_create_access");
@@ -864,6 +866,10 @@ struct buffer_head *ext3_getblk(handle_t *handle, struct inode * inode,
         if (!*errp && buffer_mapped(&dummy)) {
                 struct buffer_head *bh;
                 bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
+                if (!bh) {
+                        *errp = -EIO;
+                        goto err;
+                }
                 if (buffer_new(&dummy)) {
                         J_ASSERT(create != 0);
                         J_ASSERT(handle != 0);
@@ -896,6 +902,7 @@ struct buffer_head *ext3_getblk(handle_t *handle, struct inode * inode,
                 }
                 return bh;
         }
+err:
         return NULL;
 }
 
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)))