From 588d54039ef4c17c7bba79abe057daf5b69b2330 Mon Sep 17 00:00:00 2001 From: Wei Liu Date: Tue, 12 Aug 2014 11:59:29 +0100 Subject: [PATCH 06/14] xen-netback: fix debugfs write length check Origin: https://git.kernel.org/linus/5c807005fa60deef2db6616d9b7b24fc4c436be9 Enlarge buffer size and check input length properly, so that we don't misuse -ENOSPC. Note that command like "kickXXXX" is still allowed, that's one patch for another day if we really want to be very strict on this. Reported-by: SeeChen Ng Signed-off-by: Wei Liu Cc: Zoltan Kiss Cc: Ian Campbell Signed-off-by: David S. Miller (cherry picked from commit 5c807005fa60deef2db6616d9b7b24fc4c436be9) --- drivers/net/xen-netback/xenbus.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index 580517d..4c9041e 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -116,6 +116,7 @@ static int xenvif_read_io_ring(struct seq_file *m, void *v) } #define XENVIF_KICK_STR "kick" +#define BUFFER_SIZE 32 static ssize_t xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count, @@ -124,22 +125,24 @@ xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count, struct xenvif_queue *queue = ((struct seq_file *)filp->private_data)->private; int len; - char write[sizeof(XENVIF_KICK_STR)]; + char write[BUFFER_SIZE]; /* don't allow partial writes and check the length */ if (*ppos != 0) return 0; - if (count < sizeof(XENVIF_KICK_STR) - 1) + if (count >= sizeof(write)) return -ENOSPC; len = simple_write_to_buffer(write, - sizeof(write), + sizeof(write) - 1, ppos, buf, count); if (len < 0) return len; + write[len] = '\0'; + if (!strncmp(write, XENVIF_KICK_STR, sizeof(XENVIF_KICK_STR) - 1)) xenvif_interrupt(0, (void *)queue); else { -- 1.7.10.4