[PATCH] FS: nilfs2: potential integer overflow in nilfs_ioctl_clean_segments()

[Haogang Chen <haogangchen@gmail.com>]

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>
---
 fs/nilfs2/ioctl.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 41d6743..b805df9 100644
--- 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) {
-- 
1.7.5.4