libbpf: fix fuzzer-reported issues #3778
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Master branch: 0326074 |
This commit replace e_shnum with the elf_getshdrnum() helper to fix two
oss-fuzz-reported heap-buffer overflow in __bpf_object__open. Both
reports are incorrectly marked as fixed and while still being
reproducible in the latest libbpf.
# clusterfuzz-testcase-minimized-bpf-object-fuzzer-5747922482888704
libbpf: loading object 'fuzz-object' from buffer
libbpf: sec_cnt is 0
libbpf: elf: section(1) .data, size 0, link 538976288, flags 2020202020202020, type=2
libbpf: elf: section(2) .data, size 32, link 538976288, flags 202020202020ff20, type=1
=================================================================
==13==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6020000000c0 at pc 0x0000005a7b46 bp 0x7ffd12214af0 sp 0x7ffd12214ae8
WRITE of size 4 at 0x6020000000c0 thread T0
SCARINESS: 46 (4-byte-write-heap-buffer-overflow-far-from-bounds)
#0 0x5a7b45 in bpf_object__elf_collect /src/libbpf/src/libbpf.c:3414:24
#1 0x5733c0 in bpf_object_open /src/libbpf/src/libbpf.c:7223:16
#2 0x5739fd in bpf_object__open_mem /src/libbpf/src/libbpf.c:7263:20
...
The issue lie in libbpf's direct use of e_shnum field in ELF header as
the section header count. Where as libelf, on the other hand,
implemented an extra logic that, when e_shnum is zero and e_shoff is not
zero, will use sh_size member of the initial section header as the real
section header count (part of ELF spec to accommodate situation where
section header counter is larger than SHN_LORESERVE).
The above inconsistency lead to libbpf writing into a zero-entry calloc
area. So intead of using e_shnum directly, use the elf_getshdrnum()
helper provided by libelf to retrieve the section header counter into
sec_cnt.
Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40868
Link: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=40957
Fixes: 0d6988e ("libbpf: Fix section counting logic")
Fixes: 25bbbd7 ("libbpf: Remove assumptions about uniqueness of .rodata/.data/.bss maps")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
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Master branch: 0326074 |
When there are no program sections, obj->programs is left unallocated, and find_prog_by_sec_insn()'s search lands on &obj->programs[0] == NULL, and will cause null-pointer dereference in the following access to prog->sec_idx. Guard the search with obj->nr_programs similar to what's being done in __bpf_program__iter() to prevent null-pointer access from happening. Fixes: db2b8b0 ("libbpf: Support CO-RE relocations for multi-prog sections") Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
ELF section data pointer returned by libelf may be NULL (if section has SHT_NOBITS), so null check section data pointer before attempting to copy license and kversion section. Fixes: cb1e5e9 ("bpf tools: Collect version and license from ELF sections") Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=683771 expired. Closing PR. |
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Pull request for series with
subject: libbpf: fix fuzzer-reported issues
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=683771