From 324282c0252a44a97d628813e30ea7258940d469 Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cmaiolino@redhat.com>
Date: Thu, 9 Jan 2020 14:30:45 +0100
Subject: [PATCH] fibmap: Reject negative block numbers
Git-commit: 324282c0252a44a97d628813e30ea7258940d469
Patch-mainline: v5.6-rc1
References: bsc#1198448
FIBMAP receives an integer from userspace which is then implicitly converted
into sector_t to be passed to bmap(). No check is made to ensure userspace
didn't send a negative block number, which can end up in an underflow, and
returning to userspace a corrupted block address.
As a side-effect, the underflow caused by a negative block here, will
trigger the WARN() in iomap_bmap_actor(), which is how this issue was
first discovered.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Anthony Iliopoulos <ailiop@suse.com>
---
fs/ioctl.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 13327862f278..0be9bee9ff8f 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -65,6 +65,9 @@ static int ioctl_fibmap(struct file *filp, int __user *p)
if (error)
return error;
+ if (ur_block < 0)
+ return -EINVAL;
+
block = ur_block;
error = bmap(inode, &block);
--
2.35.1