diff mbox series

[5.10] libbpf: Handle size overflow for ringbuf mmap

Message ID 20221205113726.2208063-1-houtao1@huawei.com (mailing list archive)
State Not Applicable
Delegated to: BPF
Headers show
Series [5.10] libbpf: Handle size overflow for ringbuf mmap | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch
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Commit Message

Hou Tao Dec. 5, 2022, 11:37 a.m. UTC 
[ Upstream commit 927cbb478adf917e0a142b94baa37f06279cc466 ]

The maximum size of ringbuf is 2GB on x86-64 host, so 2 * max_entries
will overflow u32 when mapping producer page and data pages. Only
casting max_entries to size_t is not enough, because for 32-bits
application on 64-bits kernel the size of read-only mmap region
also could overflow size_t.

So fixing it by casting the size of read-only mmap region into a __u64
and checking whether or not there will be overflow during mmap.

Fixes: bf99c936f947 ("libbpf: Add BPF ring buffer support")
[houtao: return error directly and don't use libbpf_err()]
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221116072351.1168938-3-houtao@huaweicloud.com
---
Hi Greg,

Upstream commit 927cbb478adf ("libbpf: Handle size overflow for ringbuf
mmap") uses libbpf_err(), but the helper is not available for v5.10 and
picking it directly will lead to build failure as reported by kernel
test robot, so unfolding libbpf_err(). And considering libbpf in v5.10
doesn't set errno directly, so removing the setting of errno and just
returning -E2BIG.

 tools/lib/bpf/ringbuf.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 86c31c787fb9..5e242be45206 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -59,6 +59,7 @@  int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 	__u32 len = sizeof(info);
 	struct epoll_event *e;
 	struct ring *r;
+	__u64 mmap_sz;
 	void *tmp;
 	int err;
 
@@ -97,8 +98,7 @@  int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 	r->mask = info.max_entries - 1;
 
 	/* Map writable consumer page */
-	tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED,
-		   map_fd, 0);
+	tmp = mmap(NULL, rb->page_size, PROT_READ | PROT_WRITE, MAP_SHARED, map_fd, 0);
 	if (tmp == MAP_FAILED) {
 		err = -errno;
 		pr_warn("ringbuf: failed to mmap consumer page for map fd=%d: %d\n",
@@ -111,8 +111,12 @@  int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 	 * data size to allow simple reading of samples that wrap around the
 	 * end of a ring buffer. See kernel implementation for details.
 	 * */
-	tmp = mmap(NULL, rb->page_size + 2 * info.max_entries, PROT_READ,
-		   MAP_SHARED, map_fd, rb->page_size);
+	mmap_sz = rb->page_size + 2 * (__u64)info.max_entries;
+	if (mmap_sz != (__u64)(size_t)mmap_sz) {
+		pr_warn("ringbuf: ring buffer size (%u) is too big\n", info.max_entries);
+		return -E2BIG;
+	}
+	tmp = mmap(NULL, (size_t)mmap_sz, PROT_READ, MAP_SHARED, map_fd, rb->page_size);
 	if (tmp == MAP_FAILED) {
 		err = -errno;
 		ringbuf_unmap_ring(rb, r);