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ROMFS: romfs_lookup() shouldn't be doing a partial name comparison

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romfs_lookup() should be using a routine akin to strcmp() on the backing store,
rather than one akin to strncmp().  If it uses the latter, it's liable to match
/bin/shutdown when looking up /bin/sh.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells 2009-04-23 16:41:13 +01:00 committed by Linus Torvalds
parent a5422a5111
commit 84baf74bf2
3 changed files with 53 additions and 22 deletions
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4
fs/romfs/internal.h
View file

@ -43,5 +43,5 @@ extern int romfs_dev_read(struct super_block *sb, unsigned long pos,
void *buf, size_t buflen);
extern ssize_t romfs_dev_strnlen(struct super_block *sb,
unsigned long pos, size_t maxlen);
extern int romfs_dev_strncmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size);
extern int romfs_dev_strcmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size);

67
fs/romfs/storage.c
View file

@ -67,26 +67,35 @@ static ssize_t romfs_mtd_strnlen(struct super_block *sb,
* compare a string to one in a romfs image on MTD
* - return 1 if matched, 0 if differ, -ve if error
*/
static int romfs_mtd_strncmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
{
u_char buf[16];
u_char buf[17];
size_t len, segment;
int ret;
/* scan the string up to 16 bytes at a time */
/* scan the string up to 16 bytes at a time, and attempt to grab the
* trailing NUL whilst we're at it */
buf[0] = 0xff;
while (size > 0) {
segment = min_t(size_t, size, 16);
segment = min_t(size_t, size + 1, 17);
ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf);
if (ret < 0)
return ret;
len--;
if (memcmp(buf, str, len) != 0)
return 0;
buf[0] = buf[len];
size -= len;
pos += len;
str += len;
}
/* check the trailing NUL was */
if (buf[0])
return 0;
return 1;
}
#endif /* CONFIG_ROMFS_ON_MTD */
@ -154,28 +163,48 @@ static ssize_t romfs_blk_strnlen(struct super_block *sb,
* compare a string to one in a romfs image on a block device
* - return 1 if matched, 0 if differ, -ve if error
*/
static int romfs_blk_strncmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
static int romfs_blk_strcmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
{
struct buffer_head *bh;
unsigned long offset;
size_t segment;
bool x;
bool matched, terminated = false;
/* scan the string up to 16 bytes at a time */
/* compare string up to a block at a time */
while (size > 0) {
offset = pos & (ROMBSIZE - 1);
segment = min_t(size_t, size, ROMBSIZE - offset);
bh = sb_bread(sb, pos >> ROMBSBITS);
if (!bh)
return -EIO;
x = (memcmp(bh->b_data + offset, str, segment) != 0);
brelse(bh);
if (x)
return 0;
matched = (memcmp(bh->b_data + offset, str, segment) == 0);
size -= segment;
pos += segment;
str += segment;
if (matched && size == 0 && offset + segment < ROMBSIZE) {
if (!bh->b_data[offset + segment])
terminated = true;
else
matched = false;
}
brelse(bh);
if (!matched)
return 0;
}
if (!terminated) {
/* the terminating NUL must be on the first byte of the next
* block */
BUG_ON((pos & (ROMBSIZE - 1)) != 0);
bh = sb_bread(sb, pos >> ROMBSBITS);
if (!bh)
return -EIO;
matched = !bh->b_data[0];
brelse(bh);
if (!matched)
return 0;
}
return 1;
@ -234,10 +263,12 @@ ssize_t romfs_dev_strnlen(struct super_block *sb,
/*
* compare a string to one in romfs
* - the string to be compared to, str, may not be NUL-terminated; instead the
* string is of the specified size
* - return 1 if matched, 0 if differ, -ve if error
*/
int romfs_dev_strncmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
int romfs_dev_strcmp(struct super_block *sb, unsigned long pos,
const char *str, size_t size)
{
size_t limit;
@ -246,16 +277,16 @@ int romfs_dev_strncmp(struct super_block *sb, unsigned long pos,
return -EIO;
if (size > ROMFS_MAXFN)
return -ENAMETOOLONG;
if (size > limit - pos)
if (size + 1 > limit - pos)
return -EIO;
#ifdef CONFIG_ROMFS_ON_MTD
if (sb->s_mtd)
return romfs_mtd_strncmp(sb, pos, str, size);
return romfs_mtd_strcmp(sb, pos, str, size);
#endif
#ifdef CONFIG_ROMFS_ON_BLOCK
if (sb->s_bdev)
return romfs_blk_strncmp(sb, pos, str, size);
return romfs_blk_strcmp(sb, pos, str, size);
#endif
return -EIO;
}

4
fs/romfs/super.c
View file

@ -240,8 +240,8 @@ static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
goto error;
/* try to match the first 16 bytes of name */
ret = romfs_dev_strncmp(dir->i_sb, offset + ROMFH_SIZE, name,
len);
ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
len);
if (ret < 0)
goto error;
if (ret == 1)