From b71dbf1032f546bf3efd60fb5d9d0cefd200a508 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Wed, 14 Sep 2016 20:20:44 -0700
Subject: [PATCH] vfs: cap dedupe request structure size at PAGE_SIZE
Kirill A Shutemov reports that the kernel doesn't try to cap dest_count
in any way, and uses the number to allocate kernel memory. This causes
high order allocation warnings in the kernel log if someone passes in a
big enough value. We should clamp the allocation at PAGE_SIZE to avoid
stressing the VM.
The two existing users of the dedupe ioctl never send more than 120
requests, so we can safely clamp dest_range at PAGE_SIZE, because with
4k pages we can handle up to 127 dedupe candidates. Given the max
extent length of 16MB, we can end up doing 2GB of IO which is plenty.
[ Note: the "offsetof()" can't overflow, because 'count' is just a
16-bit integer. That's not obvious in the limited context of the
patch, so I'm noting it here because it made me go look. - Linus ]
Reported-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/ioctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 26aba0942a983..c415668c86d4c 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -582,6 +582,10 @@ static int ioctl_file_dedupe_range(struct file *file, void __user *arg)
}
size = offsetof(struct file_dedupe_range __user, info[count]);
+ if (size > PAGE_SIZE) {
+ ret = -ENOMEM;
+ goto out;
+ }
same = memdup_user(argp, size);
if (IS_ERR(same)) {
--
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