linux-kernel - [PATCH AUTOSEL 6.1 05/17] tomoyo: don't emit warning in tomoyo_write

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Message-Id: <20250126150353.957794-5-sashal@kernel.org>
Date: Sun, 26 Jan 2025 10:03:41 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	syzbot+7536f77535e5210a5c76@...kaller.appspotmail.com,
	Leo Stone <leocstone@...il.com>,
	Sasha Levin <sashal@...nel.org>,
	takedakn@...data.co.jp,
	paul@...l-moore.com,
	jmorris@...ei.org,
	serge@...lyn.com,
	linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 05/17] tomoyo: don't emit warning in tomoyo_write_control()

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

[ Upstream commit 3df7546fc03b8f004eee0b9e3256369f7d096685 ]

syzbot is reporting too large allocation warning at tomoyo_write_control(),
for one can write a very very long line without new line character. To fix
this warning, I use __GFP_NOWARN rather than checking for KMALLOC_MAX_SIZE,
for practically a valid line should be always shorter than 32KB where the
"too small to fail" memory-allocation rule applies.

One might try to write a valid line that is longer than 32KB, but such
request will likely fail with -ENOMEM. Therefore, I feel that separately
returning -EINVAL when a line is longer than KMALLOC_MAX_SIZE is redundant.
There is no need to distinguish over-32KB and over-KMALLOC_MAX_SIZE.

Reported-by: syzbot+7536f77535e5210a5c76@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76
Reported-by: Leo Stone <leocstone@...il.com>
Closes: https://lkml.kernel.org/r/20241216021459.178759-2-leocstone@gmail.com
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 security/tomoyo/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index a7af085550b2d..5f1cdd0af115d 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -2664,7 +2664,7 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head,
 
 		if (head->w.avail >= head->writebuf_size - 1) {
 			const int len = head->writebuf_size * 2;
-			char *cp = kzalloc(len, GFP_NOFS);
+			char *cp = kzalloc(len, GFP_NOFS | __GFP_NOWARN);
 
 			if (!cp) {
 				error = -ENOMEM;
-- 
2.39.5