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Sun, 15 Dec 2024 18:15:33 -0800 (PST) From: Leo Stone To: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com Cc: Leo Stone , jmorris@namei.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, paul@paul-moore.com, penguin-kernel@I-love.SAKURA.ne.jp, serge@hallyn.com, syzkaller-bugs@googlegroups.com, takedakn@nttdata.co.jp, tomoyo-dev-en@lists.osdn.me Subject: [PATCH] tomoyo: Reject excessively long lines Date: Sun, 15 Dec 2024 18:14:58 -0800 Message-ID: <20241216021459.178759-2-leocstone@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <675f4ea7.050a0220.37aaf.0105.GAE@google.com> References: <675f4ea7.050a0220.37aaf.0105.GAE@google.com> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 syzbot creates an anonymous memory region, and then issues a write syscall from the new memory region to a sysfs entry controlled by tomoyo, specifying a buffer size of just under 2 GB (the actual size of the buffer is ~32 MB). Because tomoyo_write_control will double the size of head->write_buf every time it runs out of space for the current line, and everything in the zero-initialized buffer is on the same line, the function will eventually issue a kzalloc with a size that is too large, triggering the warning. Reject writes with excessively long lines. Reported-by: syzbot+7536f77535e5210a5c76@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=7536f77535e5210a5c76 Signed-off-by: Leo Stone --- security/tomoyo/common.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c index 5c7b059a332a..0c75be949c9d 100644 --- a/security/tomoyo/common.c +++ b/security/tomoyo/common.c @@ -2665,6 +2665,10 @@ 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; + if (len > KMALLOC_MAX_SIZE) { + error = -EINVAL; + break; + } char *cp = kzalloc(len, GFP_NOFS); if (!cp) {