From aa3d4e015298fd523617c2bea392d02ea19eaa1a Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Mon, 9 Dec 2019 11:11:02 +0000
Subject: [PATCH] fs/adfs: bigdir: directory validation strengthening
Strengthen the directory validation by ensuring that the header fields
contain sensible values that fit inside the directory, and limit the
directory size to 4MB as per RISC OS requirements.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/adfs/dir_fplus.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/fs/adfs/dir_fplus.c b/fs/adfs/dir_fplus.c
index b83a74e9ff6d7..a2fa416fbb6d7 100644
--- a/fs/adfs/dir_fplus.c
+++ b/fs/adfs/dir_fplus.c
@@ -19,11 +19,38 @@ static unsigned int adfs_fplus_offset(const struct adfs_bigdirheader *h,
static int adfs_fplus_validate_header(const struct adfs_bigdirheader *h)
{
unsigned int size = le32_to_cpu(h->bigdirsize);
+ unsigned int len;
if (h->bigdirversion[0] != 0 || h->bigdirversion[1] != 0 ||
h->bigdirversion[2] != 0 ||
h->bigdirstartname != cpu_to_le32(BIGDIRSTARTNAME) ||
- size & 2047)
+ !size || size & 2047 || size > SZ_4M)
+ return -EIO;
+
+ size -= sizeof(struct adfs_bigdirtail) +
+ offsetof(struct adfs_bigdirheader, bigdirname);
+
+ /* Check that bigdirnamelen fits within the directory */
+ len = ALIGN(le32_to_cpu(h->bigdirnamelen), 4);
+ if (len > size)
+ return -EIO;
+
+ size -= len;
+
+ /* Check that bigdirnamesize fits within the directory */
+ len = le32_to_cpu(h->bigdirnamesize);
+ if (len > size)
+ return -EIO;
+
+ size -= len;
+
+ /*
+ * Avoid division, we know that absolute maximum number of entries
+ * can not be so large to cause overflow of the multiplication below.
+ */
+ len = le32_to_cpu(h->bigdirentries);
+ if (len > SZ_4M / sizeof(struct adfs_bigdirentry) ||
+ len * sizeof(struct adfs_bigdirentry) > size)
return -EIO;
return 0;
--
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