linux-kernel - [PATCH] bpf: btf: Fix vsnprintf return value check

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Message-ID: <20220711211317.GA1143610@laptop>
Date:   Mon, 11 Jul 2022 23:13:17 +0200
From:   Fedor Tokarev <ftokarev@...il.com>
To:     Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        ftokarev@...il.com
Subject: [PATCH] bpf: btf: Fix vsnprintf return value check

vsnprintf returns the number of characters which would have been written if
enough space had been available, excluding the terminating null byte. Thus,
the return value of 'len_left' means that the last character has been
dropped.

Signed-off-by: Fedor Tokarev <ftokarev@...il.com>
---
 kernel/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index eb12d4f705cc..a9c1c98017d4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6519,7 +6519,7 @@ static void btf_snprintf_show(struct btf_show *show, const char *fmt,
 	if (len < 0) {
 		ssnprintf->len_left = 0;
 		ssnprintf->len = len;
-	} else if (len > ssnprintf->len_left) {
+	} else if (len >= ssnprintf->len_left) {
 		/* no space, drive on to get length we would have written */
 		ssnprintf->len_left = 0;
 		ssnprintf->len += len;
-- 
2.25.1