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net: sunrpc: xprt.c: fix shift-out-of-bounds in xprt_calc_majortimeo

Message ID 20210419163603.7-1-fuzzybritches0@gmail.com (mailing list archive)
State New
Headers show
Series net: sunrpc: xprt.c: fix shift-out-of-bounds in xprt_calc_majortimeo | expand

Commit Message

Kurt Manucredo April 19, 2021, 4:36 p.m. UTC
Fix shift-out-of-bounds in xprt_calc_majortimeo().

UBSAN: shift-out-of-bounds in net/sunrpc/xprt.c:658:14
shift exponent 536871232 is too large for 64-bit type 'long u

Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
Signed-off-by: Kurt Manucredo <fuzzybritches0@gmail.com>
---
 net/sunrpc/xprt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Trond Myklebust April 19, 2021, 4:58 p.m. UTC | #1
On Mon, 2021-04-19 at 16:36 +0000, Kurt Manucredo wrote:
> Fix shift-out-of-bounds in xprt_calc_majortimeo().
> 
> UBSAN: shift-out-of-bounds in net/sunrpc/xprt.c:658:14
> shift exponent 536871232 is too large for 64-bit type 'long u
> 
> Reported-by: syzbot+ba2e91df8f74809417fa@syzkaller.appspotmail.com
> Signed-off-by: Kurt Manucredo <fuzzybritches0@gmail.com>
> ---
>  net/sunrpc/xprt.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
> index 691ccf8049a4..07128ac3d51d 100644
> --- a/net/sunrpc/xprt.c
> +++ b/net/sunrpc/xprt.c
> @@ -655,7 +655,10 @@ static unsigned long xprt_calc_majortimeo(struct
> rpc_rqst *req)
>         unsigned long majortimeo = req->rq_timeout;
>  
>         if (to->to_exponential)
> -               majortimeo <<= to->to_retries;
> +               if (to->to_retries >= sizeof(majortimeo) * 8)
> +                       majortimeo = to->to_maxval;
> +               else
> +                       majortimeo <<= to->to_retries;
>         else
>                 majortimeo += to->to_increment * to->to_retries;
>         if (majortimeo > to->to_maxval || majortimeo == 0)

I've already stated on the mailing list that I'm not accepting any
changes to xprt_calc_majortimeo() for this problem. There is a fix to
the NFS mount code that addresses this bounds issue, and that commit is
already being tested in linux-next.
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Patch

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 691ccf8049a4..07128ac3d51d 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -655,7 +655,10 @@  static unsigned long xprt_calc_majortimeo(struct rpc_rqst *req)
 	unsigned long majortimeo = req->rq_timeout;
 
 	if (to->to_exponential)
-		majortimeo <<= to->to_retries;
+		if (to->to_retries >= sizeof(majortimeo) * 8)
+			majortimeo = to->to_maxval;
+		else
+			majortimeo <<= to->to_retries;
 	else
 		majortimeo += to->to_increment * to->to_retries;
 	if (majortimeo > to->to_maxval || majortimeo == 0)