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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4606f26f1cdsm49525992f8f.11.2026.06.16.13.20.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2026 13:20:31 -0700 (PDT) Date: Tue, 16 Jun 2026 21:20:29 +0100 From: David Laight To: Naveen Kumar Chaudhary Cc: jason.wessel@windriver.com, danielt@kernel.org, dianders@chromium.org, kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kdb: use sizeof(kdb_prompt_str) instead of mismatched CMD_BUFLEN Message-ID: <20260616212029.39d35f5c@pumpkin> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 16 Jun 2026 22:14:54 +0530 Naveen Kumar Chaudhary wrote: > kdb_main.c defines CMD_BUFLEN as 200 (for command history buffers), > while kdb_io.c defines it as 256 (for kdb_prompt_str). The snprintf() > filling kdb_prompt_str incorrectly used the local CMD_BUFLEN (200), > truncating the prompt unnecessarily. Use sizeof(kdb_prompt_str) to > always match the actual buffer size. As a matter of interest what sets the string that kdbgetenv("PROMPT") returns? If it is user settable, using it as a format string doesn't seem wise (even for kdbg). David > > Signed-off-by: Naveen Kumar Chaudhary > --- > kernel/debug/kdb/kdb_main.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c > index ddce56b47b25..571e9e61b40e 100644 > --- a/kernel/debug/kdb/kdb_main.c > +++ b/kernel/debug/kdb/kdb_main.c > @@ -1265,8 +1265,8 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, > > do_full_getstr: > /* PROMPT can only be set if we have MEM_READ permission. */ > - snprintf(kdb_prompt_str, CMD_BUFLEN, kdbgetenv("PROMPT"), > - raw_smp_processor_id()); > + snprintf(kdb_prompt_str, sizeof(kdb_prompt_str), > + kdbgetenv("PROMPT"), raw_smp_processor_id()); > > /* > * Fetch command from keyboard