This makes the size argument a const, since it is always populated by
the caller. Additionally double-checks to make sure the copy_from_user
can never overflow, keeping CONFIG_DEBUG_STRICT_USER_COPY_CHECKS happy:
In function 'copy_from_user',
inlined from '__tun_chr_ioctl' at drivers/net/tun.c:1871:7:
... copy_from_user() buffer size is not provably correct
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
drivers/net/tun.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index acaaf6784179..a1f317cba206 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1855,7 +1855,7 @@ unlock:
}
static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
- unsigned long arg, int ifreq_len)
+ unsigned long arg, const size_t ifreq_len)
{
struct tun_file *tfile = file->private_data;
struct tun_struct *tun;
@@ -1869,6 +1869,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned
int cmd,
int ret;
if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || _IOC_TYPE(cmd) == 0x89) {
+ BUG_ON(ifreq_len > sizeof(ifr));
if (copy_from_user(&ifr, argp, ifreq_len))
return -EFAULT;
} else {
--
1.9.1
--
Kees Cook
Chrome OS Security
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