From 63095f4f3af59322bea984a6ae44337439348fe0 Mon Sep 17 00:00:00 2001 From: Hawkins Jiawei Date: Thu, 1 Sep 2022 00:09:38 +0800 Subject: [PATCH] ntfs: check overflow when iterating ATTR_RECORDs Kernel iterates over ATTR_RECORDs in mft record in ntfs_attr_find(). Because the ATTR_RECORDs are next to each other, kernel can get the next ATTR_RECORD from end address of current ATTR_RECORD, through current ATTR_RECORD length field. The problem is that during iteration, when kernel calculates the end address of current ATTR_RECORD, kernel may trigger an integer overflow bug in executing `a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))`. This may wrap, leading to a forever iteration on 32bit systems. This patch solves it by adding some checks on calculating end address of current ATTR_RECORD during iteration. Link: https://lkml.kernel.org/r/20220831160935.3409-4-yin31149@gmail.com Link: https://lore.kernel.org/all/20220827105842.GM2030@kadam/ Signed-off-by: Hawkins Jiawei Suggested-by: Dan Carpenter Cc: Anton Altaparmakov Cc: chenxiaosong (A) Cc: syzkaller-bugs Signed-off-by: Andrew Morton --- fs/ntfs/attrib.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c index cec4be2a2d23..a3865bc4a0c6 100644 --- a/fs/ntfs/attrib.c +++ b/fs/ntfs/attrib.c @@ -617,6 +617,14 @@ static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name, return -ENOENT; if (unlikely(!a->length)) break; + + /* check whether ATTR_RECORD's length wrap */ + if ((u8 *)a + le32_to_cpu(a->length) < (u8 *)a) + break; + /* check whether ATTR_RECORD's length is within bounds */ + if ((u8 *)a + le32_to_cpu(a->length) > mrec_end) + break; + if (a->type != type) continue; /*