On Tue, May 26, 2015 at 01:48:47PM -0400, Chuck Lever wrote:
> Ensure a proper memory access check is done by read_reset_stat(),
> then fix the following compiler warning.
>
> In file included from linux-2.6/include/net/checksum.h:25,
> from linux-2.6/include/linux/skbuff.h:31,
> from linux-2.6/include/linux/icmpv6.h:4,
> from linux-2.6/include/linux/ipv6.h:64,
> from linux-2.6/include/net/ipv6.h:16,
> from linux-2.6/include/linux/sunrpc/clnt.h:27,
> from linux-2.6/net/sunrpc/xprtrdma/svc_rdma.c:47:
> In function ‘copy_to_user’,
> inlined from ‘read_reset_stat’ at
> linux-2.6/net/sunrpc/xprtrdma/svc_rdma.c:113:
> linux-2.6/arch/x86/include/asm/uaccess.h:735: warning:
> call to ‘__copy_to_user_overflow’ declared with attribute warning:
> copy_to_user() buffer size is not provably correct
How do you get that warning? I can't hit it even with
CONFIG_USER_STRICT_USER_COPY_CHECKS set. Based on comments in arch/x86
I would have thought this would only trigger when len was a constant.
--b.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
>
> net/sunrpc/xprtrdma/svc_rdma.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/svc_rdma.c b/net/sunrpc/xprtrdma/svc_rdma.c
> index c1b6270..8eedb60 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma.c
> @@ -98,7 +98,11 @@ static int read_reset_stat(struct ctl_table *table, int write,
> else {
> char str_buf[32];
> char *data;
> - int len = snprintf(str_buf, 32, "%d\n", atomic_read(stat));
> + int len;
> +
> + if (!access_ok(VERIFY_WRITE, buffer, *lenp))
> + return -EFAULT;
> + len = snprintf(str_buf, 32, "%d\n", atomic_read(stat));
> if (len >= 32)
> return -EFAULT;
> len = strlen(str_buf);
> @@ -110,7 +114,7 @@ static int read_reset_stat(struct ctl_table *table, int write,
> len -= *ppos;
> if (len > *lenp)
> len = *lenp;
> - if (len && copy_to_user(buffer, str_buf, len))
> + if (len && __copy_to_user(buffer, str_buf, len))
> return -EFAULT;
> *lenp = len;
> *ppos += len;
--
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