Patch "bpf: Check bloom filter map value size" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    bpf: Check bloom filter map value size

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-check-bloom-filter-map-value-size.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4f37194620b9e81d10c9aeed7049a120065cade2
Author: Andrei Matei <andreimatei1@xxxxxxxxx>
Date:   Tue Mar 26 22:42:44 2024 -0400

    bpf: Check bloom filter map value size
    
    [ Upstream commit a8d89feba7e54e691ca7c4efc2a6264fa83f3687 ]
    
    This patch adds a missing check to bloom filter creating, rejecting
    values above KMALLOC_MAX_SIZE. This brings the bloom map in line with
    many other map types.
    
    The lack of this protection can cause kernel crashes for value sizes
    that overflow int's. Such a crash was caught by syzkaller. The next
    patch adds more guard-rails at a lower level.
    
    Signed-off-by: Andrei Matei <andreimatei1@xxxxxxxxx>
    Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240327024245.318299-2-andreimatei1@xxxxxxxxx
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/bpf/bloom_filter.c b/kernel/bpf/bloom_filter.c
index 48ee750849f25..78e810f49c445 100644
--- a/kernel/bpf/bloom_filter.c
+++ b/kernel/bpf/bloom_filter.c
@@ -88,6 +88,18 @@ static int bloom_map_get_next_key(struct bpf_map *map, void *key, void *next_key
 	return -EOPNOTSUPP;
 }
 
+/* Called from syscall */
+static int bloom_map_alloc_check(union bpf_attr *attr)
+{
+	if (attr->value_size > KMALLOC_MAX_SIZE)
+		/* if value_size is bigger, the user space won't be able to
+		 * access the elements.
+		 */
+		return -E2BIG;
+
+	return 0;
+}
+
 static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
 {
 	u32 bitset_bytes, bitset_mask, nr_hash_funcs, nr_bits;
@@ -196,6 +208,7 @@ static int bloom_map_check_btf(const struct bpf_map *map,
 BTF_ID_LIST_SINGLE(bpf_bloom_map_btf_ids, struct, bpf_bloom_filter)
 const struct bpf_map_ops bloom_filter_map_ops = {
 	.map_meta_equal = bpf_map_meta_equal,
+	.map_alloc_check = bloom_map_alloc_check,
 	.map_alloc = bloom_map_alloc,
 	.map_free = bloom_map_free,
 	.map_get_next_key = bloom_map_get_next_key,
diff --git a/tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c b/tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c
index d2d9e965eba59..f79815b7e951b 100644
--- a/tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c
+++ b/tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c
@@ -2,6 +2,7 @@
 /* Copyright (c) 2021 Facebook */
 
 #include <sys/syscall.h>
+#include <limits.h>
 #include <test_progs.h>
 #include "bloom_filter_map.skel.h"
 
@@ -21,6 +22,11 @@ static void test_fail_cases(void)
 	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid value size 0"))
 		close(fd);
 
+	/* Invalid value size: too big */
+	fd = bpf_map_create(BPF_MAP_TYPE_BLOOM_FILTER, NULL, 0, INT32_MAX, 100, NULL);
+	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid value too large"))
+		close(fd);
+
 	/* Invalid max entries size */
 	fd = bpf_map_create(BPF_MAP_TYPE_BLOOM_FILTER, NULL, 0, sizeof(value), 0, NULL);
 	if (!ASSERT_LT(fd, 0, "bpf_map_create bloom filter invalid max entries size"))




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