* Re: [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read()
2025-09-16 15:24 [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read() Chuck Lever
@ 2025-09-16 16:01 ` Mike Snitzer
2025-09-16 16:03 ` Chuck Lever
2025-09-17 2:33 ` NeilBrown
2025-09-17 12:25 ` Jeff Layton
2 siblings, 1 reply; 5+ messages in thread
From: Mike Snitzer @ 2025-09-16 16:01 UTC (permalink / raw)
To: Chuck Lever; +Cc: neil, jlayton, okorniev, dai.ngo, tom, linux-nfs
On Tue, Sep 16, 2025 at 11:24:19AM -0400, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>
> The *count parameter does not appear to be explicitly restricted
> to being smaller than rsize, so it might be possible to overrun
> the rq_bvec or rq_pages arrays.
>
> Rather than overrunning these arrays (damage done!) and then WARNING
> once, let's harden the loop so that it terminates before the end of
> the arrays are reached. This should result in a short read, which is
> OK -- clients recover by sending additional READ requests for the
> remaining unread bytes.
>
> Reported-by: NeilBrown <neil@brown.name>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Looks even better.
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
> ---
> fs/nfsd/vfs.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> Changes since v1:
> - Check for overrunning rq_pages as well
> - Move bounds checking to top of the loop
> - Move incrementing to the bottom of the loop
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 714777c221ed..2026431500ec 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1115,18 +1115,20 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
>
> v = 0;
> total = *count;
> - while (total) {
> + while (total && v < rqstp->rq_maxpages &&
> + rqstp->rq_next_page < rqstp->rq_page_end) {
> len = min_t(size_t, total, PAGE_SIZE - base);
> - bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++),
> + bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
> len, base);
> +
> total -= len;
> + ++rqstp->rq_next_page;
> ++v;
> base = 0;
> }
> - WARN_ON_ONCE(v > rqstp->rq_maxpages);
>
> - trace_nfsd_read_vector(rqstp, fhp, offset, *count);
> - iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count);
> + trace_nfsd_read_vector(rqstp, fhp, offset, *count - total);
> + iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count - total);
> host_err = vfs_iocb_iter_read(file, &kiocb, &iter);
> return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
> }
>
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read()
2025-09-16 16:01 ` Mike Snitzer
@ 2025-09-16 16:03 ` Chuck Lever
0 siblings, 0 replies; 5+ messages in thread
From: Chuck Lever @ 2025-09-16 16:03 UTC (permalink / raw)
To: Mike Snitzer; +Cc: neil, jlayton, okorniev, dai.ngo, tom, linux-nfs
On 9/16/25 9:01 AM, Mike Snitzer wrote:
> On Tue, Sep 16, 2025 at 11:24:19AM -0400, Chuck Lever wrote:
>> From: Chuck Lever <chuck.lever@oracle.com>
>>
>> The *count parameter does not appear to be explicitly restricted
>> to being smaller than rsize, so it might be possible to overrun
>> the rq_bvec or rq_pages arrays.
>>
>> Rather than overrunning these arrays (damage done!) and then WARNING
>> once, let's harden the loop so that it terminates before the end of
>> the arrays are reached. This should result in a short read, which is
>> OK -- clients recover by sending additional READ requests for the
>> remaining unread bytes.
>>
>> Reported-by: NeilBrown <neil@brown.name>
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>
> Looks even better.
If Neil agrees, I will fold a similar change into the direct read
patch.
> Reviewed-by: Mike Snitzer <snitzer@kernel.org>
>
>
>> ---
>> fs/nfsd/vfs.c | 12 +++++++-----
>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> Changes since v1:
>> - Check for overrunning rq_pages as well
>> - Move bounds checking to top of the loop
>> - Move incrementing to the bottom of the loop
>>
>> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
>> index 714777c221ed..2026431500ec 100644
>> --- a/fs/nfsd/vfs.c
>> +++ b/fs/nfsd/vfs.c
>> @@ -1115,18 +1115,20 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
>>
>> v = 0;
>> total = *count;
>> - while (total) {
>> + while (total && v < rqstp->rq_maxpages &&
>> + rqstp->rq_next_page < rqstp->rq_page_end) {
>> len = min_t(size_t, total, PAGE_SIZE - base);
>> - bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++),
>> + bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
>> len, base);
>> +
>> total -= len;
>> + ++rqstp->rq_next_page;
>> ++v;
>> base = 0;
>> }
>> - WARN_ON_ONCE(v > rqstp->rq_maxpages);
>>
>> - trace_nfsd_read_vector(rqstp, fhp, offset, *count);
>> - iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count);
>> + trace_nfsd_read_vector(rqstp, fhp, offset, *count - total);
>> + iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count - total);
>> host_err = vfs_iocb_iter_read(file, &kiocb, &iter);
>> return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
>> }
>>
>>
>>
--
Chuck Lever
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read()
2025-09-16 15:24 [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read() Chuck Lever
2025-09-16 16:01 ` Mike Snitzer
@ 2025-09-17 2:33 ` NeilBrown
2025-09-17 12:25 ` Jeff Layton
2 siblings, 0 replies; 5+ messages in thread
From: NeilBrown @ 2025-09-17 2:33 UTC (permalink / raw)
To: Chuck Lever; +Cc: jlayton, okorniev, dai.ngo, tom, linux-nfs
On Wed, 17 Sep 2025, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>
> The *count parameter does not appear to be explicitly restricted
> to being smaller than rsize, so it might be possible to overrun
> the rq_bvec or rq_pages arrays.
>
> Rather than overrunning these arrays (damage done!) and then WARNING
> once, let's harden the loop so that it terminates before the end of
> the arrays are reached. This should result in a short read, which is
> OK -- clients recover by sending additional READ requests for the
> remaining unread bytes.
>
> Reported-by: NeilBrown <neil@brown.name>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> fs/nfsd/vfs.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> Changes since v1:
> - Check for overrunning rq_pages as well
> - Move bounds checking to top of the loop
> - Move incrementing to the bottom of the loop
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 714777c221ed..2026431500ec 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1115,18 +1115,20 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
>
> v = 0;
> total = *count;
> - while (total) {
> + while (total && v < rqstp->rq_maxpages &&
> + rqstp->rq_next_page < rqstp->rq_page_end) {
> len = min_t(size_t, total, PAGE_SIZE - base);
> - bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++),
> + bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
> len, base);
> +
> total -= len;
> + ++rqstp->rq_next_page;
> ++v;
> base = 0;
> }
> - WARN_ON_ONCE(v > rqstp->rq_maxpages);
>
> - trace_nfsd_read_vector(rqstp, fhp, offset, *count);
> - iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count);
> + trace_nfsd_read_vector(rqstp, fhp, offset, *count - total);
> + iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count - total);
> host_err = vfs_iocb_iter_read(file, &kiocb, &iter);
> return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
> }
Very nice - thanks.
Reviewed-by: NeilBrown <neil@brown.name>
NeilBrown
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read()
2025-09-16 15:24 [PATCH v2] NFSD: Add array bounds-checking in nfsd_iter_read() Chuck Lever
2025-09-16 16:01 ` Mike Snitzer
2025-09-17 2:33 ` NeilBrown
@ 2025-09-17 12:25 ` Jeff Layton
2 siblings, 0 replies; 5+ messages in thread
From: Jeff Layton @ 2025-09-17 12:25 UTC (permalink / raw)
To: Chuck Lever, neil, okorniev, dai.ngo, tom; +Cc: linux-nfs
On Tue, 2025-09-16 at 11:24 -0400, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
>
> The *count parameter does not appear to be explicitly restricted
> to being smaller than rsize, so it might be possible to overrun
> the rq_bvec or rq_pages arrays.
>
> Rather than overrunning these arrays (damage done!) and then WARNING
> once, let's harden the loop so that it terminates before the end of
> the arrays are reached. This should result in a short read, which is
> OK -- clients recover by sending additional READ requests for the
> remaining unread bytes.
>
> Reported-by: NeilBrown <neil@brown.name>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> fs/nfsd/vfs.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> Changes since v1:
> - Check for overrunning rq_pages as well
> - Move bounds checking to top of the loop
> - Move incrementing to the bottom of the loop
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 714777c221ed..2026431500ec 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1115,18 +1115,20 @@ __be32 nfsd_iter_read(struct svc_rqst *rqstp, struct svc_fh *fhp,
>
> v = 0;
> total = *count;
> - while (total) {
> + while (total && v < rqstp->rq_maxpages &&
> + rqstp->rq_next_page < rqstp->rq_page_end) {
> len = min_t(size_t, total, PAGE_SIZE - base);
> - bvec_set_page(&rqstp->rq_bvec[v], *(rqstp->rq_next_page++),
> + bvec_set_page(&rqstp->rq_bvec[v], *rqstp->rq_next_page,
> len, base);
> +
> total -= len;
> + ++rqstp->rq_next_page;
> ++v;
> base = 0;
> }
> - WARN_ON_ONCE(v > rqstp->rq_maxpages);
>
> - trace_nfsd_read_vector(rqstp, fhp, offset, *count);
> - iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count);
> + trace_nfsd_read_vector(rqstp, fhp, offset, *count - total);
> + iov_iter_bvec(&iter, ITER_DEST, rqstp->rq_bvec, v, *count - total);
> host_err = vfs_iocb_iter_read(file, &kiocb, &iter);
> return nfsd_finish_read(rqstp, fhp, file, offset, count, eof, host_err);
> }
>
Much nicer.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread