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authorDavid Howells <dhowells@redhat.com>2022-03-11 13:24:08 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-11 10:17:12 -0800
commit96a4d8912b28451cd62825fd7caa0e66e091d938 (patch)
treeec33ef611f80cf43cb840f4213a56245362d2bba
parentc1853fbadcba1497f4907971e7107888e0714c81 (diff)
downloadlwn-96a4d8912b28451cd62825fd7caa0e66e091d938.tar.gz
lwn-96a4d8912b28451cd62825fd7caa0e66e091d938.zip
watch_queue: Fix to always request a pow-of-2 pipe ring size
The pipe ring size must always be a power of 2 as the head and tail pointers are masked off by AND'ing with the size of the ring - 1. watch_queue_set_size(), however, lets you specify any number of notes between 1 and 511. This number is passed through to pipe_resize_ring() without checking/forcing its alignment. Fix this by rounding the number of slots required up to the nearest power of two. The request is meant to guarantee that at least that many notifications can be generated before the queue is full, so rounding down isn't an option, but, alternatively, it may be better to give an error if we aren't allowed to allocate that much ring space. Fixes: c73be61cede5 ("pipe: Add general notification queue support") Reported-by: Jann Horn <jannh@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/watch_queue.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index dfb3a7e28280..4bcd400984a7 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -244,7 +244,7 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
goto error;
}
- ret = pipe_resize_ring(pipe, nr_notes);
+ ret = pipe_resize_ring(pipe, roundup_pow_of_two(nr_notes));
if (ret < 0)
goto error;