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libbpf: fix string comparison for guessing eBPF program type 

libbpf is able to deduce the type of a program from the name of the ELF
section in which it is located. However, the comparison is made on the
first n characters, n being determined with sizeof() applied to the
reference string (e.g. "xdp"). When such section names are supposed to
receive a suffix separated with a slash (e.g. "kprobe/"), using sizeof()
takes the final NUL character of the reference string into account,
which implies that both strings must be equal. Instead, the desired
behaviour would consist in taking the length of the string, *without*
accounting for the ending NUL character, and to make sure the reference
string is a prefix to the ELF section name.

Subtract 1 to the total size of the string for obtaining the length for
the comparison.

Fixes: 583c90097f ("libbpf: add ability to guess program type based on section name")
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
hifive-unleashed-5.1
Quentin Monnet 2018-01-16 15:51:48 -08:00 committed by Daniel Borkmann
parent 39b72ccdb2
commit d77be68955
1 changed files with 1 additions and 1 deletions
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tools/lib/bpf/libbpf.c
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@ -1803,7 +1803,7 @@ BPF_PROG_TYPE_FNS(tracepoint, BPF_PROG_TYPE_TRACEPOINT);
BPF_PROG_TYPE_FNS(xdp, BPF_PROG_TYPE_XDP);
BPF_PROG_TYPE_FNS(perf_event, BPF_PROG_TYPE_PERF_EVENT);
#define BPF_PROG_SEC(string, type) { string, sizeof(string), type }
#define BPF_PROG_SEC(string, type) { string, sizeof(string) - 1, type }
static const struct {
const char *sec;
size_t len;