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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id j20sm3638718pfd.106.2021.01.06.15.46.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Jan 2021 15:46:40 -0800 (PST) Date: Wed, 6 Jan 2021 15:46:39 -0800 From: Kees Cook To: Xiaoming Ni Cc: linux-kernel@vger.kernel.org, mcgrof@kernel.org, yzaikin@google.com, adobriyan@gmail.com, vbabka@suse.cz, linux-fsdevel@vger.kernel.org, mhocko@suse.com, mhiramat@kernel.org, wangle6@huawei.com Subject: Re: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters. Message-ID: <202101061539.966EBB293@keescook> References: <20201224074256.117413-1-nixiaoming@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201224074256.117413-1-nixiaoming@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org subject typo: "sysclt" -> "sysctl" On Thu, Dec 24, 2020 at 03:42:56PM +0800, Xiaoming Ni wrote: > The process_sysctl_arg() does not check whether val is empty before > invoking strlen(val). If the command line parameter () is incorrectly > configured and val is empty, oops is triggered. > > For example, "hung_task_panic=1" is incorrectly written as "hung_task_panic". > > log: > Kernel command line: .... hung_task_panic > .... > [000000000000000n] user address but active_mm is swapper > Internal error: Oops: 96000005 [#1] SMP > Modules linked in: > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.10.1 #1 > Hardware name: linux,dummy-virt (DT) > pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--) > pc : __pi_strlen+0x10/0x98 > lr : process_sysctl_arg+0x1e4/0x2ac > sp : ffffffc01104bd40 > x29: ffffffc01104bd40 x28: 0000000000000000 > x27: ffffff80c0a4691e x26: ffffffc0102a7c8c > x25: 0000000000000000 x24: ffffffc01104be80 > x23: ffffff80c22f0b00 x22: ffffff80c02e28c0 > x21: ffffffc0109f9000 x20: 0000000000000000 > x19: ffffffc0107c08de x18: 0000000000000003 > x17: ffffffc01105d000 x16: 0000000000000054 > x15: ffffffffffffffff x14: 3030253078413830 > x13: 000000000000ffff x12: 0000000000000000 > x11: 0101010101010101 x10: 0000000000000005 > x9 : 0000000000000003 x8 : ffffff80c0980c08 > x7 : 0000000000000000 x6 : 0000000000000002 > x5 : ffffff80c0235000 x4 : ffffff810f7c7ee0 > x3 : 000000000000043a x2 : 00bdcc4ebacf1a54 > x1 : 0000000000000000 x0 : 0000000000000000 > Call trace: > __pi_strlen+0x10/0x98 > parse_args+0x278/0x344 > do_sysctl_args+0x8c/0xfc > kernel_init+0x5c/0xf4 > ret_from_fork+0x10/0x30 > Code: b200c3eb 927cec01 f2400c07 54000301 (a8c10c22) > > Fixes: 3db978d480e2843 ("kernel/sysctl: support setting sysctl parameters > from kernel command line") > Signed-off-by: Xiaoming Ni > --- > fs/proc/proc_sysctl.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c > index 317899222d7f..4516411a2b44 100644 > --- a/fs/proc/proc_sysctl.c > +++ b/fs/proc/proc_sysctl.c > @@ -1757,6 +1757,9 @@ static int process_sysctl_arg(char *param, char *val, > loff_t pos = 0; > ssize_t wret; > > + if (!val) > + return 0; > + > if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) { > param += sizeof("sysctl") - 1; Otherwise, yeah, this is a good test to add. I would make it more verbose, though: if (!val) { pr_err("Missing param value! Expected '%s=...value...'\n", param); return 0; } -- Kees Cook