linux-kernel - [PATCH 5.15 350/779] libbpf: fix an snprintf() overflow check

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Date:   Mon, 15 Aug 2022 19:59:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 350/779] libbpf: fix an snprintf() overflow check

From: Dan Carpenter <dan.carpenter@...cle.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@...cle.com>
Acked-by: Martin KaFai Lau <kafai@...com>
Link: https://lore.kernel.org/r/YtZ+oAySqIhFl6/J@kili
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.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 33c19590ee43..4435c09fe132 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -480,7 +480,7 @@ 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