From: Gianfranco Trad <gianf.trad@xxxxxxxxx> [ Upstream commit 264db9d666ad9a35075cc9ed9ec09d021580fbb1 ] Check for overflow when computing alen in udf_current_aext to mitigate later uninit-value use in udf_get_fileshortad KMSAN bug[1]. After applying the patch reproducer did not trigger any issue[2]. [1] https://syzkaller.appspot.com/bug?extid=8901c4560b7ab5c2f9df [2] https://syzkaller.appspot.com/x/log.txt?x=10242227980000 Reported-by: syzbot+8901c4560b7ab5c2f9df@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=8901c4560b7ab5c2f9df Tested-by: syzbot+8901c4560b7ab5c2f9df@xxxxxxxxxxxxxxxxxxxxxxxxx Suggested-by: Jan Kara <jack@xxxxxxxx> Signed-off-by: Gianfranco Trad <gianf.trad@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Link: https://patch.msgid.link/20240925074613.8475-3-gianf.trad@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/udf/inode.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/udf/inode.c b/fs/udf/inode.c index 80dae442ecd72..53511c726d575 100644 --- a/fs/udf/inode.c +++ b/fs/udf/inode.c @@ -2257,12 +2257,15 @@ int udf_current_aext(struct inode *inode, struct extent_position *epos, alen = udf_file_entry_alloc_offset(inode) + iinfo->i_lenAlloc; } else { + struct allocExtDesc *header = + (struct allocExtDesc *)epos->bh->b_data; + if (!epos->offset) epos->offset = sizeof(struct allocExtDesc); ptr = epos->bh->b_data + epos->offset; - alen = sizeof(struct allocExtDesc) + - le32_to_cpu(((struct allocExtDesc *)epos->bh->b_data)-> - lengthAllocDescs); + if (check_add_overflow(sizeof(struct allocExtDesc), + le32_to_cpu(header->lengthAllocDescs), &alen)) + return -1; } switch (iinfo->i_alloc_type) { -- 2.43.0
