In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf: Harden bloom filter sizing and indexing on 32-bit kernels<\/p>\n
bloom_map_alloc() has two 32-bit-specific problems when the computed
\nbitmap reaches the U32_MAX fallback case.<\/p>\n
First, BITS_TO_BYTES(U32_MAX) is evaluated with 32-bit arithmetic. The
\naddition performed by DIV_ROUND_UP wraps, so the map allocates only the
\nfixed-size bloom filter object while keeping bitset_mask == U32_MAX.
\nSubsequent updates can then write past the allocated object.<\/p>\n
Second, fixing only the allocation size is not sufficient. The bloom hash
\nis a u32, but set_bit() takes a signed long bit number and x86 test_bit()
\neventually feeds the index to variable_test_bit(long, …). On 32-bit
\nkernels, hashes in [0x80000000, U32_MAX] therefore become negative bit
\noffsets. x86 bt\/bts with a memory operand interpret those offsets relative
\nto the supplied base, so a map with bitset_mask == U32_MAX can read or
\nwrite before bloom->bitset even after allocating the full 512 MiB bitmap.<\/p>\n
Keep the U32_MAX fallback, but split each hash into a word pointer and an
\nin-word bit number before calling test_bit() or set_bit(). The bitops
\nargument is then always in [0, BITS_PER_LONG – 1], while BIT_WORD(h) still
\nselects the intended word in the full bitmap.<\/p>\n
Compute the bitset size from (u64)bitset_mask + 1 before passing the final
\nsize to bpf_map_area_alloc(). This fixes the original under-allocation and
\nkeeps the allocated storage consistent with the addressable bitset.<\/p>\n
Exploitation note: local privilege escalation is possible on a 32-bit x86
\nkernel using the under-allocation bug from a binary with CAP_BPF.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf: Harden bloom filter sizing and indexing on 32-bit kernels<\/p>\n
bloom_map_alloc() has two 32-bit-specific problems when the compute<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21501","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21501","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21501"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}