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From: Cengiz Can <cengiz@kernel.wtf>
To: sumit.garg@linaro.org
Cc: andriy.shevchenko@linux.intel.com, cengiz@kernel.wtf,
	daniel.thompson@linaro.org, dianders@chromium.org,
	jason.wessel@windriver.com, kgdb-bugreport@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, pmladek@suse.com
Subject: [PATCH v3] kdb: remove unnecessary null check of dbg_io_ops
Date: Tue, 30 Jun 2020 11:29:23 +0300	[thread overview]
Message-ID: <20200630082922.28672-1-cengiz@kernel.wtf> (raw)
In-Reply-To: <CAFA6WYNpCG2xPERd=NeKf+EthbX+1R4iieOL52kWnBp8y_+Nbw@mail.gmail.com>

`kdb_msg_write` operates on a global `struct kgdb_io *` called
`dbg_io_ops`.

It's initialized in `debug_core.c` and checked throughout the debug
flow.

There's a null check in `kdb_msg_write` which triggers static analyzers
and gives the (almost entirely wrong) impression that it can be null.

Coverity scanner caught this as CID 1465042.

I have removed the unnecessary null check and eliminated false-positive
forward null dereference warning.

Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
---
 kernel/debug/kdb/kdb_io.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 683a799618ad..81783ecaec58 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -545,18 +545,18 @@ static int kdb_search_string(char *searched, char *searchfor)
 static void kdb_msg_write(const char *msg, int msg_len)
 {
 	struct console *c;
+	const char *cp;
+	int len;
 
 	if (msg_len == 0)
 		return;
 
-	if (dbg_io_ops) {
-		const char *cp = msg;
-		int len = msg_len;
+	cp = msg;
+	len = msg_len;
 
-		while (len--) {
-			dbg_io_ops->write_char(*cp);
-			cp++;
-		}
+	while (len--) {
+		dbg_io_ops->write_char(*cp);
+		cp++;
 	}
 
 	for_each_console(c) {
-- 
2.27.0


  reply	other threads:[~2020-06-30  8:30 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29 13:59 [PATCH] kdb: prevent possible null deref in kdb_msg_write Cengiz Can
2020-06-29 14:27 ` Daniel Thompson
2020-06-29 14:50 ` Petr Mladek
2020-06-29 14:53   ` Petr Mladek
2020-06-29 15:37   ` Daniel Thompson
2020-06-29 20:50     ` [PATCH v2] kdb: remove unnecessary null check of dbg_io_ops Cengiz Can
2020-06-29 21:16       ` Doug Anderson
2020-06-29 22:10         ` Cengiz Can
2020-06-30  5:55     ` [PATCH] kdb: prevent possible null deref in kdb_msg_write Sumit Garg
2020-06-30  8:29       ` Cengiz Can [this message]
2020-06-30 11:36         ` [PATCH v3] kdb: remove unnecessary null check of dbg_io_ops Sumit Garg
2020-06-30 11:48           ` Andy Shevchenko
2020-06-30 22:32         ` Doug Anderson
2020-07-10 12:15           ` Cengiz Can
2020-07-10 13:41             ` Daniel Thompson

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