2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------ data exposure From: Jamie Iles <[email protected]> CVE-2012-4508 kernel: ext4: AIO vs fallocate stale data exposure [dannf: backported to Debian's 2.6.32] Signed-off-by: Willy Tarreau <[email protected]> --- fs/ext4/extents.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 66 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index f4b471d..3f022ea 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -62,6 +62,7 @@ ext4_fsblk_t ext_pblock(struct ext4_extent *ex) * idx_pblock: * combine low and high parts of a leaf physical block number into ext4_fsblk_t */ +#define EXT4_EXT_DATA_VALID 0x8 /* extent contains valid data */ ext4_fsblk_t idx_pblock(struct ext4_extent_idx *ix) { ext4_fsblk_t block; @@ -2933,6 +2934,30 @@ static int ext4_split_unwritten_extents(handle_t *handle, ext4_ext_mark_uninitialized(ex3); err = ext4_ext_insert_extent(handle, inode, path, ex3, flags); if (err == -ENOSPC && may_zeroout) { + /* + * This is different from the upstream, because we + * need only a flag to say that the extent contains + * the actual data. + * + * If the extent contains valid data, which can only + * happen if AIO races with fallocate, then we got + * here from ext4_convert_unwritten_extents_dio(). + * So we have to be careful not to zeroout valid data + * in the extent. + * + * To avoid it, we only zeroout the ex3 and extend the + * extent which is going to become initialized to cover + * ex3 as well. and continue as we would if only + * split in two was required. + */ + if (flags & EXT4_EXT_DATA_VALID) { + err = ext4_ext_zeroout(inode, ex3); + if (err) + goto fix_extent_len; + max_blocks = allocated; + ex2->ee_len = cpu_to_le16(max_blocks); + goto skip; + } err = ext4_ext_zeroout(inode, &orig_ex); if (err) goto fix_extent_len; @@ -2978,6 +3003,7 @@ static int ext4_split_unwritten_extents(handle_t *handle, allocated = max_blocks; } +skip: /* * If there was a change of depth as part of the * insertion of ex3 above, we need to update the length @@ -3030,11 +3056,16 @@ fix_extent_len: ext4_ext_dirty(handle, inode, path + depth); return err; } + static int ext4_convert_unwritten_extents_dio(handle_t *handle, struct inode *inode, + ext4_lblk_t iblock, + unsigned int max_blocks, struct ext4_ext_path *path) { struct ext4_extent *ex; + ext4_lblk_t ee_block; + unsigned int ee_len; struct ext4_extent_header *eh; int depth; int err = 0; @@ -3043,6 +3074,30 @@ static int ext4_convert_unwritten_extents_dio(handle_t *handle, depth = ext_depth(inode); eh = path[depth].p_hdr; ex = path[depth].p_ext; + ee_block = le32_to_cpu(ex->ee_block); + ee_len = ext4_ext_get_actual_len(ex); + + ext_debug("ext4_convert_unwritten_extents_endio: inode %lu, logical" + "block %llu, max_blocks %u\n", inode->i_ino, + (unsigned long long)ee_block, ee_len); + + /* If extent is larger than requested then split is required */ + + if (ee_block != iblock || ee_len > max_blocks) { + err = ext4_split_unwritten_extents(handle, inode, path, + iblock, max_blocks, + EXT4_EXT_DATA_VALID); + if (err < 0) + goto out; + ext4_ext_drop_refs(path); + path = ext4_ext_find_extent(inode, iblock, path); + if (IS_ERR(path)) { + err = PTR_ERR(path); + goto out; + } + depth = ext_depth(inode); + ex = path[depth].p_ext; + } err = ext4_ext_get_access(handle, inode, path + depth); if (err) @@ -3129,7 +3184,8 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode, /* async DIO end_io complete, convert the filled extent to written */ if (flags == EXT4_GET_BLOCKS_DIO_CONVERT_EXT) { ret = ext4_convert_unwritten_extents_dio(handle, inode, - path); + iblock, max_blocks, + path); if (ret >= 0) ext4_update_inode_fsync_trans(handle, inode, 1); goto out2; @@ -3498,6 +3554,12 @@ void ext4_ext_truncate(struct inode *inode) int err = 0; /* + * finish any pending end_io work so we won't run the risk of + * converting any truncated blocks to initialized later + */ + flush_aio_dio_completed_IO(inode); + + /* * probably first extent we're gonna free will be last in block */ err = ext4_writepage_trans_blocks(inode); @@ -3630,6 +3692,9 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len) mutex_unlock(&inode->i_mutex); return ret; } + + /* Prevent race condition between unwritten */ + flush_aio_dio_completed_IO(inode); retry: while (ret >= 0 && ret < max_blocks) { block = block + ret; -- 1.7.12.2.21.g234cd45.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
