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ext4: Avoid crashing on NULL ptr dereference on a filesystem error

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If the EOFBLOCK_FL flag is set when it should not be and the inode is
zero length, then eh_entries is zero, and ex is NULL, so dereferencing
ex to print ex->ee_block causes a kernel OOPS in
ext4_ext_map_blocks().

On top of that, the error message which is printed isn't very helpful.
So we fix this by printing something more explanatory which doesn't
involve trying to print ex->ee_block.

Addresses-Google-Bug: #2655740

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o
2010-05-16 23:00:00 -04:00
parent 12e9b89200
commit f70f362b4a
1 changed files with 5 additions and 4 deletions
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9
fs/ext4/extents.c
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@@ -3370,8 +3370,9 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
*/ */
if (unlikely(path[depth].p_ext == NULL && depth != 0)) { if (unlikely(path[depth].p_ext == NULL && depth != 0)) {
EXT4_ERROR_INODE(inode, "bad extent address " EXT4_ERROR_INODE(inode, "bad extent address "
"iblock: %d, depth: %d pblock %lld", "lblock: %lu, depth: %d pblock %lld",
map->m_lblk, depth, path[depth].p_block); (unsigned long) map->m_lblk, depth,
path[depth].p_block);
err = -EIO; err = -EIO;
goto out2; goto out2;
} }
@@ -3501,8 +3502,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
if (unlikely(ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))) { if (unlikely(ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))) {
if (unlikely(!eh->eh_entries)) { if (unlikely(!eh->eh_entries)) {
EXT4_ERROR_INODE(inode, EXT4_ERROR_INODE(inode,
"eh->eh_entries == 0 ee_block %d", "eh->eh_entries == 0 and "
ex->ee_block); "EOFBLOCKS_FL set");
err = -EIO; err = -EIO;
goto out2; goto out2;
} }