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@xxxxxx> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx> --- fs/ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/ioctl.c b/fs/ioctl.c index 83f36feaf781..79468b5a6391 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); -- 2.23.0
