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ext4: Make extents code sanely handle on-disk corruption
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Add more run-time checking of extent header fields and remove BUG_ON
checks so we don't panic the kernel just because the on-disk filesystem
is corrupted.

Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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Alex Tomas authored and Theodore Ts'o committed Jul 18, 2007
1 parent ff9ddf7 commit c29c0ae
Showing 1 changed file with 86 additions and 58 deletions.
144 changes: 86 additions & 58 deletions fs/ext4/extents.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -92,36 +92,6 @@ static void ext4_idx_store_pblock(struct ext4_extent_idx *ix, ext4_fsblk_t pb)
ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
}

static int ext4_ext_check_header(const char *function, struct inode *inode,
struct ext4_extent_header *eh)
{
const char *error_msg = NULL;

if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
error_msg = "invalid magic";
goto corrupted;
}
if (unlikely(eh->eh_max == 0)) {
error_msg = "invalid eh_max";
goto corrupted;
}
if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
error_msg = "invalid eh_entries";
goto corrupted;
}
return 0;

corrupted:
ext4_error(inode->i_sb, function,
"bad header in inode #%lu: %s - magic %x, "
"entries %u, max %u, depth %u",
inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
le16_to_cpu(eh->eh_depth));

return -EIO;
}

static handle_t *ext4_ext_journal_restart(handle_t *handle, int needed)
{
int err;
Expand Down Expand Up @@ -270,6 +240,70 @@ static int ext4_ext_space_root_idx(struct inode *inode)
return size;
}

static int
ext4_ext_max_entries(struct inode *inode, int depth)
{
int max;

if (depth == ext_depth(inode)) {
if (depth == 0)
max = ext4_ext_space_root(inode);
else
max = ext4_ext_space_root_idx(inode);
} else {
if (depth == 0)
max = ext4_ext_space_block(inode);
else
max = ext4_ext_space_block_idx(inode);
}

return max;
}

static int __ext4_ext_check_header(const char *function, struct inode *inode,
struct ext4_extent_header *eh,
int depth)
{
const char *error_msg;
int max = 0;

if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
error_msg = "invalid magic";
goto corrupted;
}
if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
error_msg = "unexpected eh_depth";
goto corrupted;
}
if (unlikely(eh->eh_max == 0)) {
error_msg = "invalid eh_max";
goto corrupted;
}
max = ext4_ext_max_entries(inode, depth);
if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
error_msg = "too large eh_max";
goto corrupted;
}
if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
error_msg = "invalid eh_entries";
goto corrupted;
}
return 0;

corrupted:
ext4_error(inode->i_sb, function,
"bad header in inode #%lu: %s - magic %x, "
"entries %u, max %u(%u), depth %u(%u)",
inode->i_ino, error_msg, le16_to_cpu(eh->eh_magic),
le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
max, le16_to_cpu(eh->eh_depth), depth);

return -EIO;
}

#define ext4_ext_check_header(inode, eh, depth) \
__ext4_ext_check_header(__FUNCTION__, inode, eh, depth)

#ifdef EXT_DEBUG
static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
{
Expand Down Expand Up @@ -330,16 +364,14 @@ static void ext4_ext_drop_refs(struct ext4_ext_path *path)
/*
* ext4_ext_binsearch_idx:
* binary search for the closest index of the given block
* the header must be checked before calling this
*/
static void
ext4_ext_binsearch_idx(struct inode *inode, struct ext4_ext_path *path, int block)
{
struct ext4_extent_header *eh = path->p_hdr;
struct ext4_extent_idx *r, *l, *m;

BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
BUG_ON(le16_to_cpu(eh->eh_entries) <= 0);

ext_debug("binsearch for %d(idx): ", block);

Expand Down Expand Up @@ -389,16 +421,14 @@ ext4_ext_binsearch_idx(struct inode *inode, struct ext4_ext_path *path, int bloc
/*
* ext4_ext_binsearch:
* binary search for closest extent of the given block
* the header must be checked before calling this
*/
static void
ext4_ext_binsearch(struct inode *inode, struct ext4_ext_path *path, int block)
{
struct ext4_extent_header *eh = path->p_hdr;
struct ext4_extent *r, *l, *m;

BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);
BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));

if (eh->eh_entries == 0) {
/*
* this leaf is empty:
Expand Down Expand Up @@ -469,11 +499,10 @@ ext4_ext_find_extent(struct inode *inode, int block, struct ext4_ext_path *path)
short int depth, i, ppos = 0, alloc = 0;

eh = ext_inode_hdr(inode);
BUG_ON(eh == NULL);
if (ext4_ext_check_header(__FUNCTION__, inode, eh))
depth = ext_depth(inode);
if (ext4_ext_check_header(inode, eh, depth))
return ERR_PTR(-EIO);

i = depth = ext_depth(inode);

/* account possible depth increase */
if (!path) {
Expand All @@ -485,10 +514,12 @@ ext4_ext_find_extent(struct inode *inode, int block, struct ext4_ext_path *path)
}
path[0].p_hdr = eh;

i = depth;
/* walk through the tree */
while (i) {
ext_debug("depth %d: num %d, max %d\n",
ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));

ext4_ext_binsearch_idx(inode, path + ppos, block);
path[ppos].p_block = idx_pblock(path[ppos].p_idx);
path[ppos].p_depth = i;
Expand All @@ -505,7 +536,7 @@ ext4_ext_find_extent(struct inode *inode, int block, struct ext4_ext_path *path)
path[ppos].p_hdr = eh;
i--;

if (ext4_ext_check_header(__FUNCTION__, inode, eh))
if (ext4_ext_check_header(inode, eh, i))
goto err;
}

Expand All @@ -514,9 +545,6 @@ ext4_ext_find_extent(struct inode *inode, int block, struct ext4_ext_path *path)
path[ppos].p_ext = NULL;
path[ppos].p_idx = NULL;

if (ext4_ext_check_header(__FUNCTION__, inode, eh))
goto err;

/* find extent */
ext4_ext_binsearch(inode, path + ppos, block);

Expand Down Expand Up @@ -1738,13 +1766,12 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
unsigned uninitialized = 0;
struct ext4_extent *ex;

/* the header must be checked already in ext4_ext_remove_space() */
ext_debug("truncate since %lu in leaf\n", start);
if (!path[depth].p_hdr)
path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
eh = path[depth].p_hdr;
BUG_ON(eh == NULL);
BUG_ON(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max));
BUG_ON(eh->eh_magic != EXT4_EXT_MAGIC);

/* find where to start removing */
ex = EXT_LAST_EXTENT(eh);
Expand Down Expand Up @@ -1898,7 +1925,7 @@ int ext4_ext_remove_space(struct inode *inode, unsigned long start)
return -ENOMEM;
}
path[0].p_hdr = ext_inode_hdr(inode);
if (ext4_ext_check_header(__FUNCTION__, inode, path[0].p_hdr)) {
if (ext4_ext_check_header(inode, path[0].p_hdr, depth)) {
err = -EIO;
goto out;
}
Expand All @@ -1919,17 +1946,8 @@ int ext4_ext_remove_space(struct inode *inode, unsigned long start)
if (!path[i].p_hdr) {
ext_debug("initialize header\n");
path[i].p_hdr = ext_block_hdr(path[i].p_bh);
if (ext4_ext_check_header(__FUNCTION__, inode,
path[i].p_hdr)) {
err = -EIO;
goto out;
}
}

BUG_ON(le16_to_cpu(path[i].p_hdr->eh_entries)
> le16_to_cpu(path[i].p_hdr->eh_max));
BUG_ON(path[i].p_hdr->eh_magic != EXT4_EXT_MAGIC);

if (!path[i].p_idx) {
/* this level hasn't been touched yet */
path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
Expand All @@ -1946,17 +1964,27 @@ int ext4_ext_remove_space(struct inode *inode, unsigned long start)
i, EXT_FIRST_INDEX(path[i].p_hdr),
path[i].p_idx);
if (ext4_ext_more_to_rm(path + i)) {
struct buffer_head *bh;
/* go to the next level */
ext_debug("move to level %d (block %llu)\n",
i + 1, idx_pblock(path[i].p_idx));
memset(path + i + 1, 0, sizeof(*path));
path[i+1].p_bh =
sb_bread(sb, idx_pblock(path[i].p_idx));
if (!path[i+1].p_bh) {
bh = sb_bread(sb, idx_pblock(path[i].p_idx));
if (!bh) {
/* should we reset i_size? */
err = -EIO;
break;
}
if (WARN_ON(i + 1 > depth)) {
err = -EIO;
break;
}
if (ext4_ext_check_header(inode, ext_block_hdr(bh),
depth - i - 1)) {
err = -EIO;
break;
}
path[i + 1].p_bh = bh;

/* save actual number of indexes since this
* number is changed at the next iteration */
Expand Down

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