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libbpf: Fix section counting logic

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e_shnum does include section #0 and as such is exactly the number of ELF
sections that we need to allocate memory for to use section indices as
array indices. Fix the off-by-one error.

This is purely accounting fix, previously we were overallocating one
too many array items. But no correctness errors otherwise.

Fixes: 25bbbd7a44 ("libbpf: Remove assumptions about uniqueness of .rodata/.data/.bss maps")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20211103173213.1376990-5-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2021-11-03 10:32:12 -07:00 committed by Alexei Starovoitov
parent 62554d52e7
commit 0d6988e16a
1 changed files with 4 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
tools/lib/bpf/libbpf.c
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@ -3190,11 +3190,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
Elf_Scn *scn; Elf_Scn *scn;
Elf64_Shdr *sh; Elf64_Shdr *sh;
/* ELF section indices are 1-based, so allocate +1 element to keep /* ELF section indices are 0-based, but sec #0 is special "invalid"
* indexing simple. Also include 0th invalid section into sec_cnt for * section. e_shnum does include sec #0, so e_shnum is the necessary
* simpler and more traditional iteration logic. * size of an array to keep all the sections.
*/ */
obj->efile.sec_cnt = 1 + obj->efile.ehdr->e_shnum; obj->efile.sec_cnt = obj->efile.ehdr->e_shnum;
obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs)); obj->efile.secs = calloc(obj->efile.sec_cnt, sizeof(*obj->efile.secs));
if (!obj->efile.secs) if (!obj->efile.secs)
return -ENOMEM; return -ENOMEM;