[PATCH 5.18 0484/1095] libbpf: fix an snprintf() overflow check

Greg Kroah-Hartman
2022-08-15T21:19:49Z

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit b77ffb30cfc5f58e957571d8541c6a7e3da19221 ]

The snprintf() function returns the number of bytes it *would* have
copied if there were enough space. So it can return > the
sizeof(gen->attach_target).

Fixes: 67234743736a ("libbpf: Generate loader program out of BPF ELF file.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/YtZ+oAySqIhFl6/J@kili
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/gen_loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
index 927745b08014..23f5c46708f8 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -533,7 +533,7 @@ void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *attach_name,
gen->attach_kind = kind;
ret = snprintf(gen->attach_target, sizeof(gen->attach_target), "%s%s",
prefix, attach_name);
- if (ret == sizeof(gen->attach_target))
+ if (ret >= sizeof(gen->attach_target))
gen->error = -ENOSPC;
}

--
2.35.1