>From 1e0d4adf17e7ef03281d7b16555e7c1508c8ed2d Mon Sep 17 00:00:00 2001 From: Vladislav Efanov Date: Thu, 2 Feb 2023 17:04:56 +0300 Subject: [PATCH] udf: Check consistency of Space Bitmap Descriptor Bits, which are related to Bitmap Descriptor logical blocks, are not reset when buffer headers are allocated for them. As the result, these logical blocks can be treated as free and be used for other blocks.This can cause usage of one buffer header for several types of data. UDF issues WARNING in this situation: WARNING: CPU: 0 PID: 2703 at fs/udf/inode.c:2014 __udf_add_aext+0x685/0x7d0 fs/udf/inode.c:2014 RIP: 0010:__udf_add_aext+0x685/0x7d0 fs/udf/inode.c:2014 Call Trace: udf_setup_indirect_aext+0x573/0x880 fs/udf/inode.c:1980 udf_add_aext+0x208/0x2e0 fs/udf/inode.c:2067 udf_insert_aext fs/udf/inode.c:2233 [inline] udf_update_extents fs/udf/inode.c:1181 [inline] inode_getblk+0x1981/0x3b70 fs/udf/inode.c:885 Found by Linux Verification Center (linuxtesting.org) with syzkaller. [JK: Somewhat cleaned up the boundary checks] Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Vladislav Efanov Signed-off-by: Jan Kara --- fs/udf/balloc.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c index cdf90928b7f2..14b9db4c80f0 100644 --- a/fs/udf/balloc.c +++ b/fs/udf/balloc.c @@ -36,18 +36,41 @@ static int read_block_bitmap(struct super_block *sb, unsigned long bitmap_nr) { struct buffer_head *bh = NULL; - int retval = 0; + int i; + int max_bits, off, count; struct kernel_lb_addr loc; loc.logicalBlockNum = bitmap->s_extPosition; loc.partitionReferenceNum = UDF_SB(sb)->s_partition; bh = sb_bread(sb, udf_get_lb_pblock(sb, &loc, block)); + bitmap->s_block_bitmap[bitmap_nr] = bh; if (!bh) - retval = -EIO; + return -EIO; - bitmap->s_block_bitmap[bitmap_nr] = bh; - return retval; + /* Check consistency of Space Bitmap buffer. */ + max_bits = sb->s_blocksize * 8; + if (!bitmap_nr) { + off = sizeof(struct spaceBitmapDesc) << 3; + count = min(max_bits - off, bitmap->s_nr_groups); + } else { + /* + * Rough check if bitmap number is too big to have any bitmap + * blocks reserved. + */ + if (bitmap_nr > + (bitmap->s_nr_groups >> (sb->s_blocksize_bits + 3)) + 2) + return 0; + off = 0; + count = bitmap->s_nr_groups - bitmap_nr * max_bits + + (sizeof(struct spaceBitmapDesc) << 3); + count = min(count, max_bits); + } + + for (i = 0; i < count; i++) + if (udf_test_bit(i + off, bh->b_data)) + return -EFSCORRUPTED; + return 0; } static int __load_block_bitmap(struct super_block *sb, -- 2.35.3