linux-kernel - [PATCH] kdb: Fix a potential buffer overflow in kdb

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Message-Id: <0b1790ca91b71e3362a6a4c2863bc5787b4d60c9.1698501284.git.christophe.jaillet@wanadoo.fr>
Date:   Sat, 28 Oct 2023 15:55:00 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Martin Hicks <mort@....com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        kgdb-bugreport@...ts.sourceforge.net
Subject: [PATCH] kdb: Fix a potential buffer overflow in kdb_local()

When appending "[defcmd]" to 'kdb_prompt_str', the size of the string
already in the buffer should be taken into account.

Switch from strncat() to strlcat() which does the correct test to avoid
such an overflow.

Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 kernel/debug/kdb/kdb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 438b868cbfa9..e5f0bf0f45d1 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1350,7 +1350,7 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs,
 		snprintf(kdb_prompt_str, CMD_BUFLEN, kdbgetenv("PROMPT"),
 			 raw_smp_processor_id());
 		if (defcmd_in_progress)
-			strncat(kdb_prompt_str, "[defcmd]", CMD_BUFLEN);
+			strlcat(kdb_prompt_str, "[defcmd]", CMD_BUFLEN);
 
 		/*
 		 * Fetch command from keyboard
-- 
2.34.1