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authorDarrick J. Wong <darrick.wong@oracle.com>2016-09-14 20:20:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-15 13:29:52 -0700
commitb71dbf1032f546bf3efd60fb5d9d0cefd200a508 (patch)
tree6b09fe48b1c87c94f8274be6e834dc6abada6c63
parent5297e0f0fe13305a1fc7f01986be0dccd063d57a (diff)
downloadlinux-stericsson-b71dbf1032f546bf3efd60fb5d9d0cefd200a508.tar.gz
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>
-rw-r--r--fs/ioctl.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 26aba0942a98..c415668c86d4 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)) {