nilfs2: potential integer overflow in nilfs_ioctl_clean_segments()

There is a potential integer overflow in nilfs_ioctl_clean_segments().
When a large argv[n].v_nmembs is passed from the userspace, the subsequent
call to vmalloc() will allocate a buffer smaller than expected, which
leads to out-of-bound access in nilfs_ioctl_move_blocks() and
lfs_clean_segments().

The following check does not prevent the overflow because nsegs is also
controlled by the userspace and could be very large.

		if (argv[n].v_nmembs > nsegs * nilfs->ns_blocks_per_segment)
			goto out_free;

This patch clamps argv[n].v_nmembs to UINT_MAX / argv[n].v_size, and
returns -EINVAL when overflow.

Signed-off-by: Haogang Chen <haogangchen@gmail.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 3e654273cfc28e04bf6c3dd608314eeef7c5ab9b..ac258beeda3c4e3e9a3a36a375619838c8c7a350 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -625,6 +625,9 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
                if (argv[n].v_nmembs > nsegs * nilfs->ns_blocks_per_segment)
                        goto out_free;
 
+               if (argv[n].v_nmembs >= UINT_MAX / argv[n].v_size)
+                       goto out_free;
+
                len = argv[n].v_size * argv[n].v_nmembs;
                base = (void __user *)(unsigned long)argv[n].v_base;
                if (len == 0) {