4.14-stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
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 Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/ext4/xattr.c | 26 +++++++++++++++++++------- fs/ext4/xattr.h | 11 +++++++++++ 2 files changed, 30 insertions(+), 7 deletions(-)
--- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -196,7 +196,7 @@ ext4_xattr_check_entries(struct ext4_xat while (!IS_LAST_ENTRY(entry)) { u32 size = le32_to_cpu(entry->e_value_size);
- if (size > INT_MAX) + if (size > EXT4_XATTR_SIZE_MAX) return -EFSCORRUPTED;
if (size != 0 && entry->e_value_inum == 0) { @@ -539,8 +539,10 @@ ext4_xattr_block_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; if (size > buffer_size) goto cleanup; if (entry->e_value_inum) { @@ -549,8 +551,12 @@ ext4_xattr_block_get(struct inode *inode if (error) goto cleanup; } else { - memcpy(buffer, bh->b_data + - le16_to_cpu(entry->e_value_offs), size); + u16 offset = le16_to_cpu(entry->e_value_offs); + void *p = bh->b_data + offset; + + if (unlikely(p + size > end)) + goto cleanup; + memcpy(buffer, p, size); } } error = size; @@ -588,8 +594,10 @@ 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; if (size > buffer_size) goto cleanup; if (entry->e_value_inum) { @@ -598,8 +606,12 @@ ext4_xattr_ibody_get(struct inode *inode if (error) goto cleanup; } else { - memcpy(buffer, (void *)IFIRST(header) + - le16_to_cpu(entry->e_value_offs), size); + u16 offset = le16_to_cpu(entry->e_value_offs); + void *p = (void *)IFIRST(header) + offset; + + if (unlikely(p + size > end)) + goto cleanup; + memcpy(buffer, p, size); } } error = size; --- a/fs/ext4/xattr.h +++ b/fs/ext4/xattr.h @@ -71,6 +71,17 @@ struct ext4_xattr_entry { #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) + +/* * The minimum size of EA value when you start storing it in an external inode * size of block - size of header - size of 1 entry - 4 null bytes */