Hello Oleg,
Thank you for the review.
On 3/7/2025 8:21 PM, Oleg Nesterov wrote:
On 03/07, K Prateek Nayak wrote:
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1271,6 +1271,10 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
struct pipe_buffer *bufs;
unsigned int head, tail, mask, n;
+ /* nr_slots larger than limits of pipe->{head,tail} */
+ if (unlikely(nr_slots > (pipe_index_t)-1u))
+ return -EINVAL;
The whole series look "obviously" good to me,
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
-------------------------------------------------------------------------------
But damn ;) lets look at round_pipe_size(),
unsigned int round_pipe_size(unsigned int size)
{
if (size > (1U << 31))
return 0;
/* Minimum pipe size, as required by POSIX */
if (size < PAGE_SIZE)
return PAGE_SIZE;
return roundup_pow_of_two(size);
}
it is a bit silly to allow the maximum size == 1U << 31 in pipe_set_size()
or (more importantly) in /proc/sys/fs/pipe-max-size, and then nack nr_slots
in pipe_resize_ring().
So perhaps this check should go into round_pipe_size() ? Although I can't
suggest a simple/clear check without unnecesary restrictions for the case
when pipe_index_t is u16.
pipe_resize_ring() has another caller, watch_queue_set_size(), but it has
its own hard limits...
"nr_notes" for watch queues cannot cross 512 so we should be covered there.
As for round_pipe_size(), we can do:
diff --git a/fs/pipe.c b/fs/pipe.c
index ce1af7592780..f82098aaa510 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1253,6 +1253,8 @@ const struct file_operations pipefifo_fops = {
*/
unsigned int round_pipe_size(unsigned int size)
{
+ unsigned int max_slots;
+
if (size > (1U << 31))
return 0;
@@ -1260,7 +1262,14 @@ unsigned int round_pipe_size(unsigned int size)
if (size < PAGE_SIZE)
return PAGE_SIZE;
- return roundup_pow_of_two(size);
+ size = roundup_pow_of_two(size);
+ max_slots = size >> PAGE_SHIFT;
+
+ /* Max slots cannot be covered pipe->{head,tail} limits */
+ if (max_slots > (pipe_index_t)-1U)
+ return 0;
+
+ return size;
}
/*
--
Since pipe_resize_ring() can be called without actually looking at
"pipe_max_size" as is the case with watch queues, we can either keep the
check in pipe_resize_ring() as well out of paranoia or get rid of it
since the current users are within the bounds.
Thoughts?
Oleg.
--
Thanks and Regards,
Prateek
