[PATCH v2 1/4] fs/pipe: Limit the slots in pipe_resize_ring()

K Prateek Nayak
2025-03-07T05:30:01Z

Limit the number of slots in pipe_resize_ring() to the maximum value
representable by pipe->{head,tail}. Values beyond the max limit can
lead to incorrect pipe occupancy related calculations where the pipe
will never appear full.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
---
Changelog:

RFC v1..v2:

o Use (pipe_index_t)-1u as the limit instead of BITS_PER_TYPE()
hackery. (Oleg)

o Added the "Suggested-by:" tag.
---
fs/pipe.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/pipe.c b/fs/pipe.c
index 4d0799e4e719..88e81f84e3ea 100644
--- 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;
+
bufs = kcalloc(nr_slots, sizeof(*bufs),
GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
if (unlikely(!bufs))
--
2.43.0