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authorTheodore Ts'o <tytso@mit.edu>2010-10-28 05:30:08 +0400
committerTheodore Ts'o <tytso@mit.edu>2010-10-28 05:30:08 +0400
commit8941ec8bb6443d28d5c25311870aeaa809cf1538 (patch)
tree5fbd2aff55ff077ec98604b03f6fc9d35a6f081d /fs/ext4
parent640e9396566a1e1f52f2db294755a23f1e62cc97 (diff)
downloadlinux-8941ec8bb6443d28d5c25311870aeaa809cf1538.tar.xz
ext4: avoid uninitialized memory references in ext3_htree_next_block()
If the first block of htree directory is missing '.' or '..' but is otherwise a valid directory, and we do a lookup for '.' or '..', it's possible to dereference an uninitialized memory pointer in ext4_htree_next_block(). We avoid this by moving the special case from ext4_dx_find_entry() to ext4_find_entry(); this also means we can optimize ext4_find_entry() slightly when NFS looks up "..". Thanks to Brad Spengler for pointing a Clang warning that led me to look more closely at this code. The warning was harmless, but it was useful in pointing out code that was too ugly to live. This warning was also reported by Roman Borisov. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: Brad Spengler <spender@grsecurity.net>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/namei.c30
1 files changed, 15 insertions, 15 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 314c0d3b3fa9..213523803dff 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -856,6 +856,7 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
struct buffer_head *bh_use[NAMEI_RA_SIZE];
struct buffer_head *bh, *ret = NULL;
ext4_lblk_t start, block, b;
+ const u8 *name = d_name->name;
int ra_max = 0; /* Number of bh's in the readahead
buffer, bh_use[] */
int ra_ptr = 0; /* Current index into readahead
@@ -870,6 +871,16 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
namelen = d_name->len;
if (namelen > EXT4_NAME_LEN)
return NULL;
+ if ((namelen <= 2) && (name[0] == '.') &&
+ (name[1] == '.' || name[1] == '0')) {
+ /*
+ * "." or ".." will only be in the first block
+ * NFS may look up ".."; "." should be handled by the VFS
+ */
+ block = start = 0;
+ nblocks = 1;
+ goto restart;
+ }
if (is_dx(dir)) {
bh = ext4_dx_find_entry(dir, d_name, res_dir, &err);
/*
@@ -960,9 +971,8 @@ cleanup_and_exit:
static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct qstr *d_name,
struct ext4_dir_entry_2 **res_dir, int *err)
{
- struct super_block * sb;
+ struct super_block * sb = dir->i_sb;
struct dx_hash_info hinfo;
- u32 hash;
struct dx_frame frames[2], *frame;
struct ext4_dir_entry_2 *de, *top;
struct buffer_head *bh;
@@ -971,18 +981,8 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct q
int namelen = d_name->len;
const u8 *name = d_name->name;
- sb = dir->i_sb;
- /* NFS may look up ".." - look at dx_root directory block */
- if (namelen > 2 || name[0] != '.'||(name[1] != '.' && name[1] != '\0')){
- if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err)))
- return NULL;
- } else {
- frame = frames;
- frame->bh = NULL; /* for dx_release() */
- frame->at = (struct dx_entry *)frames; /* hack for zero entry*/
- dx_set_block(frame->at, 0); /* dx_root block is 0 */
- }
- hash = hinfo.hash;
+ if (!(frame = dx_probe(d_name, dir, &hinfo, frames, err)))
+ return NULL;
do {
block = dx_get_block(frame->at);
if (!(bh = ext4_bread (NULL,dir, block, 0, err)))
@@ -1008,7 +1008,7 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir, const struct q
}
brelse(bh);
/* Check to see if we should continue to search */
- retval = ext4_htree_next_block(dir, hash, frame,
+ retval = ext4_htree_next_block(dir, hinfo.hash, frame,
frames, NULL);
if (retval < 0) {
ext4_warning(sb,