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ext4: add extra checks to ext4_xattr_block_get() 

commit 54dd0e0a1b255f115f8647fc6fb93273251b01b9 upstream.

Add explicit checks in ext4_xattr_block_get() just in case the
e_value_offs and e_value_size fields in the the xattr block are
corrupted in memory after the buffer_verified bit is set on the xattr
block.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
[bwh: Backported to 3.16:
 - Drop change to ext4_xattr_check_entries() which is only needed for the
   xattr-in-inode case
 - Adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Theodore Ts'o 2018-03-30 20:04:11 -04:00 committed by syphyr
parent 9abd5e1cad
commit 5412a3ef79
2 changed files with 29 additions and 6 deletions
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24
fs/ext4/xattr.c
View File

@ -333,12 +333,18 @@ bad_block:
if (error)
goto cleanup;
size = le32_to_cpu(entry->e_value_size);
error = -ERANGE;
if (unlikely(size > EXT4_XATTR_SIZE_MAX))
goto cleanup;
if (buffer) {
error = -ERANGE;
u16 offset = le16_to_cpu(entry->e_value_offs);
void *p = bh->b_data + offset;
if (size > buffer_size)
goto cleanup;
memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
size);
if (unlikely(p + size > end))
goto cleanup;
memcpy(buffer, p, size);
}
error = size;
@ -376,12 +382,18 @@ ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
if (error)
goto cleanup;
size = le32_to_cpu(entry->e_value_size);
error = -ERANGE;
if (unlikely(size > EXT4_XATTR_SIZE_MAX))
goto cleanup;
if (buffer) {
error = -ERANGE;
u16 offset = le16_to_cpu(entry->e_value_offs);
void *p = (void *)IFIRST(header) + offset;
if (size > buffer_size)
goto cleanup;
memcpy(buffer, (void *)IFIRST(header) +
le16_to_cpu(entry->e_value_offs), size);
if (unlikely(p + size > end))
goto cleanup;
memcpy(buffer, p, size);
}
error = size;

11
fs/ext4/xattr.h
View File

@ -67,6 +67,17 @@ struct ext4_xattr_entry {
EXT4_I(inode)->i_extra_isize))
#define IFIRST(hdr) ((struct ext4_xattr_entry *)((hdr)+1))
/*
* XATTR_SIZE_MAX is currently 64k, but for the purposes of checking
* for file system consistency errors, we use a somewhat bigger value.
* This allows XATTR_SIZE_MAX to grow in the future, but by using this
* instead of INT_MAX for certain consistency checks, we don't need to
* worry about arithmetic overflows. (Actually XATTR_SIZE_MAX is
* defined in include/uapi/linux/limits.h, so changing it is going
* not going to be trivial....)
*/
#define EXT4_XATTR_SIZE_MAX (1 << 24)
#define BHDR(bh) ((struct ext4_xattr_header *)((bh)->b_data))
#define ENTRY(ptr) ((struct ext4_xattr_entry *)(ptr))
#define BFIRST(bh) ENTRY(BHDR(bh)+1)