0aa7d66395
- Fix out-of-bound heap write (boo#1194248 boo#1194249 CVE-2021-45940 CVE-2021-45941) + libbpf-Use-elf_getshdrnum-instead-of-e_shnum.patch - Fix use-after-free in btf_dump_name_dups (boo#1204391 CVE-2022-3534) + libbpf-Fix-use-after-free-in-btf_dump_name_dups.patch - Fix memory leak in parse_usdt_arg() (boo#1204393 CVE-2022-3533) + libbpf-Fix-memory-leak-in-parse_usdt_arg.patch - Fix null pointer dereference in find_prog_by_sec_insn() (boo#1204502 CVE-2022-3606) + libbpf-Fix-null-pointer-dereference-in-find_prog_by_.patch OBS-URL: https://build.opensuse.org/request/show/1034422 OBS-URL: https://build.opensuse.org/package/show/devel:libraries:c_c++/libbpf?expand=0&rev=25
83 lines
3.6 KiB
Diff
83 lines
3.6 KiB
Diff
From 741277511035893c72a34df05da3b943afa747a4 Mon Sep 17 00:00:00 2001
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From: Shung-Hsi Yu <shung-hsi.yu@suse.com>
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Date: Wed, 12 Oct 2022 10:23:51 +0800
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Subject: [PATCH 3/3] libbpf: Use elf_getshdrnum() instead of e_shnum
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This commit replace e_shnum with the elf_getshdrnum() helper to fix two
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oss-fuzz-reported heap-buffer overflow in __bpf_object__open. Both
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reports are incorrectly marked as fixed and while still being
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reproducible in the latest libbpf.
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# clusterfuzz-testcase-minimized-bpf-object-fuzzer-5747922482888704
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libbpf: loading object 'fuzz-object' from buffer
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libbpf: sec_cnt is 0
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libbpf: elf: section(1) .data, size 0, link 538976288, flags 2020202020202020, type=2
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libbpf: elf: section(2) .data, size 32, link 538976288, flags 202020202020ff20, type=1
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=================================================================
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==13==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6020000000c0 at pc 0x0000005a7b46 bp 0x7ffd12214af0 sp 0x7ffd12214ae8
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WRITE of size 4 at 0x6020000000c0 thread T0
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SCARINESS: 46 (4-byte-write-heap-buffer-overflow-far-from-bounds)
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#0 0x5a7b45 in bpf_object__elf_collect /src/libbpf/src/libbpf.c:3414:24
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#1 0x5733c0 in bpf_object_open /src/libbpf/src/libbpf.c:7223:16
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#2 0x5739fd in bpf_object__open_mem /src/libbpf/src/libbpf.c:7263:20
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...
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The issue lie in libbpf's direct use of e_shnum field in ELF header as
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the section header count. Where as libelf implemented an extra logic
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that, when e_shnum == 0 && e_shoff != 0, will use sh_size member of the
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initial section header as the real section header count (part of ELF
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spec to accommodate situation where section header counter is larger
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than SHN_LORESERVE).
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The above inconsistency lead to libbpf writing into a zero-entry calloc
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area. So intead of using e_shnum directly, use the elf_getshdrnum()
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helper provided by libelf to retrieve the section header counter into
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sec_cnt.
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Fixes: 0d6988e16a12 ("libbpf: Fix section counting logic")
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Fixes: 25bbbd7a444b ("libbpf: Remove assumptions about uniqueness of .rodata/.data/.bss maps")
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Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40868
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Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40957
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Link: https://lore.kernel.org/bpf/20221012022353.7350-2-shung-hsi.yu@suse.com
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---
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src/libbpf.c | 13 +++++++++----
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1 file changed, 9 insertions(+), 4 deletions(-)
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diff --git a/src/libbpf.c b/src/libbpf.c
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index 184ce16..2e8ac13 100644
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--- a/src/libbpf.c
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+++ b/src/libbpf.c
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@@ -597,7 +597,7 @@ struct elf_state {
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size_t shstrndx; /* section index for section name strings */
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size_t strtabidx;
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struct elf_sec_desc *secs;
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- int sec_cnt;
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+ size_t sec_cnt;
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int btf_maps_shndx;
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__u32 btf_maps_sec_btf_id;
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int text_shndx;
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@@ -3312,10 +3312,15 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
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Elf64_Shdr *sh;
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/* ELF section indices are 0-based, but sec #0 is special "invalid"
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- * section. e_shnum does include sec #0, so e_shnum is the necessary
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- * size of an array to keep all the sections.
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+ * section. Since section count retrieved by elf_getshdrnum() does
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+ * include sec #0, it is already the necessary size of an array to keep
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+ * all the sections.
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*/
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- obj->efile.sec_cnt = obj->efile.ehdr->e_shnum;
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+ if (elf_getshdrnum(obj->efile.elf, &obj->efile.sec_cnt)) {
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+ pr_warn("elf: failed to get the number of sections for %s: %s\n",
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+ obj->path, elf_errmsg(-1));
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+ return -LIBBPF_ERRNO__FORMAT;
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+ }
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obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs));
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if (!obj->efile.secs)
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return -ENOMEM;
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--
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2.38.0
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