From bf2b63535ebafae27b95b370df95749d5bde6b04 Mon Sep 17 00:00:00 2001 From: Peter Marko Date: Tue, 6 May 2025 19:51:11 +0200 Subject: libbpf: patch CVE-2025-29481 Backport patch which mentions PoC [1] which is also linked from [2]. [1] https://github.com/libbpf/libbpf/commit/806b4e0a9f658d831119cece11a082ba1578b800 [2] https://nvd.nist.gov/vuln/detail/CVE-2025-29481 Signed-off-by: Peter Marko Signed-off-by: Khem Raj --- .../libbpf/files/CVE-2025-29481.patch | 102 +++++++++++++++++++++ meta-oe/recipes-kernel/libbpf/libbpf_1.5.0.bb | 1 + 2 files changed, 103 insertions(+) create mode 100644 meta-oe/recipes-kernel/libbpf/files/CVE-2025-29481.patch diff --git a/meta-oe/recipes-kernel/libbpf/files/CVE-2025-29481.patch b/meta-oe/recipes-kernel/libbpf/files/CVE-2025-29481.patch new file mode 100644 index 0000000000..ebfcb94a2f --- /dev/null +++ b/meta-oe/recipes-kernel/libbpf/files/CVE-2025-29481.patch @@ -0,0 +1,102 @@ +From 806b4e0a9f658d831119cece11a082ba1578b800 Mon Sep 17 00:00:00 2001 +From: Viktor Malik +Date: Tue, 15 Apr 2025 17:50:14 +0200 +Subject: [PATCH] libbpf: Fix buffer overflow in bpf_object__init_prog + +As shown in [1], it is possible to corrupt a BPF ELF file such that +arbitrary BPF instructions are loaded by libbpf. This can be done by +setting a symbol (BPF program) section offset to a large (unsigned) +number such that
overflows and points +before the section data in the memory. + +Consider the situation below where: +- prog_start = sec_start + symbol_offset <-- size_t overflow here +- prog_end = prog_start + prog_size + + prog_start sec_start prog_end sec_end + | | | | + v v v v + .....................|################################|............ + +The report in [1] also provides a corrupted BPF ELF which can be used as +a reproducer: + + $ readelf -S crash + Section Headers: + [Nr] Name Type Address Offset + Size EntSize Flags Link Info Align + ... + [ 2] uretprobe.mu[...] PROGBITS 0000000000000000 00000040 + 0000000000000068 0000000000000000 AX 0 0 8 + + $ readelf -s crash + Symbol table '.symtab' contains 8 entries: + Num: Value Size Type Bind Vis Ndx Name + ... + 6: ffffffffffffffb8 104 FUNC GLOBAL DEFAULT 2 handle_tp + +Here, the handle_tp prog has section offset ffffffffffffffb8, i.e. will +point before the actual memory where section 2 is allocated. + +This is also reported by AddressSanitizer: + + ================================================================= + ==1232==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7c7302fe0000 at pc 0x7fc3046e4b77 bp 0x7ffe64677cd0 sp 0x7ffe64677490 + READ of size 104 at 0x7c7302fe0000 thread T0 + #0 0x7fc3046e4b76 in memcpy (/lib64/libasan.so.8+0xe4b76) + #1 0x00000040df3e in bpf_object__init_prog /src/libbpf/src/libbpf.c:856 + #2 0x00000040df3e in bpf_object__add_programs /src/libbpf/src/libbpf.c:928 + #3 0x00000040df3e in bpf_object__elf_collect /src/libbpf/src/libbpf.c:3930 + #4 0x00000040df3e in bpf_object_open /src/libbpf/src/libbpf.c:8067 + #5 0x00000040f176 in bpf_object__open_file /src/libbpf/src/libbpf.c:8090 + #6 0x000000400c16 in main /poc/poc.c:8 + #7 0x7fc3043d25b4 in __libc_start_call_main (/lib64/libc.so.6+0x35b4) + #8 0x7fc3043d2667 in __libc_start_main@@GLIBC_2.34 (/lib64/libc.so.6+0x3667) + #9 0x000000400b34 in _start (/poc/poc+0x400b34) + + 0x7c7302fe0000 is located 64 bytes before 104-byte region [0x7c7302fe0040,0x7c7302fe00a8) + allocated by thread T0 here: + #0 0x7fc3046e716b in malloc (/lib64/libasan.so.8+0xe716b) + #1 0x7fc3045ee600 in __libelf_set_rawdata_wrlock (/lib64/libelf.so.1+0xb600) + #2 0x7fc3045ef018 in __elf_getdata_rdlock (/lib64/libelf.so.1+0xc018) + #3 0x00000040642f in elf_sec_data /src/libbpf/src/libbpf.c:3740 + +The problem here is that currently, libbpf only checks that the program +end is within the section bounds. There used to be a check +`while (sec_off < sec_sz)` in bpf_object__add_programs, however, it was +removed by commit 6245947c1b3c ("libbpf: Allow gaps in BPF program +sections to support overriden weak functions"). + +Add a check for detecting the overflow of `sec_off + prog_sz` to +bpf_object__init_prog to fix this issue. + +[1] https://github.com/lmarch2/poc/blob/main/libbpf/libbpf.md + +Fixes: 6245947c1b3c ("libbpf: Allow gaps in BPF program sections to support overriden weak functions") +Reported-by: lmarch2 <2524158037@qq.com> +Signed-off-by: Viktor Malik +Signed-off-by: Andrii Nakryiko +Reviewed-by: Shung-Hsi Yu +Link: https://github.com/lmarch2/poc/blob/main/libbpf/libbpf.md +Link: https://lore.kernel.org/bpf/20250415155014.397603-1-vmalik@redhat.com + +CVE: CVE-2025-29481 +Upstream-Status: Backport [https://github.com/libbpf/libbpf/commit/806b4e0a9f658d831119cece11a082ba1578b800] +Signed-off-by: Peter Marko +--- + src/libbpf.c | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +diff --git a/src/libbpf.c b/src/libbpf.c +index b2591f5..56250b5 100644 +--- a/src/libbpf.c ++++ b/src/libbpf.c +@@ -889,7 +889,7 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, + return -LIBBPF_ERRNO__FORMAT; + } + +- if (sec_off + prog_sz > sec_sz) { ++ if (sec_off + prog_sz > sec_sz || sec_off + prog_sz < sec_off) { + pr_warn("sec '%s': program at offset %zu crosses section boundary\n", + sec_name, sec_off); + return -LIBBPF_ERRNO__FORMAT; diff --git a/meta-oe/recipes-kernel/libbpf/libbpf_1.5.0.bb b/meta-oe/recipes-kernel/libbpf/libbpf_1.5.0.bb index 58bb7bca09..45caca0114 100644 --- a/meta-oe/recipes-kernel/libbpf/libbpf_1.5.0.bb +++ b/meta-oe/recipes-kernel/libbpf/libbpf_1.5.0.bb @@ -10,6 +10,7 @@ DEPENDS = "zlib elfutils" SRC_URI = "git://github.com/libbpf/libbpf.git;protocol=https;branch=master \ file://0001-libbpf-check-for-empty-BTF-data-section-in-btf_parse.patch \ + file://CVE-2025-29481.patch;striplevel=2 \ " SRCREV = "09b9e83102eb8ab9e540d36b4559c55f3bcdb95d" -- cgit v1.2.3-54-g00ecf