| From: Theodore Ts'o <tytso@mit.edu> |
| Date: Fri, 30 Mar 2018 20:04:11 -0400 |
| Subject: 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> |
| --- |
| --- a/fs/ext4/xattr.c |
| +++ b/fs/ext4/xattr.c |
| @@ -327,12 +327,18 @@ 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; |
| |
| @@ -370,12 +376,18 @@ ext4_xattr_ibody_get(struct inode *inode |
| 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; |
| |
| --- a/fs/ext4/xattr.h |
| +++ b/fs/ext4/xattr.h |
| @@ -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) |