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SubjectRe: [PATCH] Test for sb_getblk return value
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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>

--
=====================================
Glauber de Oliveira Costa
IBM Linux Technology Center - Brazil
glommer@br.ibm.com
=====================================diff -Naurp linux-2.6.14-rc2-orig/fs/ext2/inode.c linux-2.6.14-rc2-cleanp/fs/ext2/inode.c
--- linux-2.6.14-rc2-orig/fs/ext2/inode.c 2005-10-19 02:04:12.000000000 +0000
+++ linux-2.6.14-rc2-cleanp/fs/ext2/inode.c 2005-10-19 12:07:12.000000000 +0000
@@ -440,6 +440,10 @@ static int ext2_alloc_branch(struct inod
* 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 -Naurp linux-2.6.14-rc2-orig/fs/ext3/inode.c linux-2.6.14-rc2-cleanp/fs/ext3/inode.c
--- linux-2.6.14-rc2-orig/fs/ext3/inode.c 2005-10-19 02:04:12.000000000 +0000
+++ linux-2.6.14-rc2-cleanp/fs/ext3/inode.c 2005-10-19 02:03:22.000000000 +0000
@@ -523,7 +523,6 @@ static int ext3_alloc_branch(handle_t *h
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 *h
* 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
if (!*errp && buffer_mapped(&dummy)) {
struct buffer_head *bh;
bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
+ if (!bh) {
+ *errp = -EIO;
+ return NULL;
+ }
if (buffer_new(&dummy)) {
J_ASSERT(create != 0);
J_ASSERT(handle != 0);
diff -Naurp linux-2.6.14-rc2-orig/fs/ext3/resize.c linux-2.6.14-rc2-cleanp/fs/ext3/resize.c
--- linux-2.6.14-rc2-orig/fs/ext3/resize.c 2005-10-19 02:04:12.000000000 +0000
+++ linux-2.6.14-rc2-cleanp/fs/ext3/resize.c 2005-10-19 01:54:47.000000000 +0000
@@ -118,6 +118,8 @@ static struct buffer_head *bclean(handle
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
ext3_debug("update backup group %#04lx (+%d)\n", block, bit);

gdb = sb_getblk(sb, block);
+ if (!bh) {
+ 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_
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)))
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