2020-12-24 07:44:48

by Xiaoming Ni

Subject: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters.

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 <[email protected]>
---
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;

--
2.27.0

2021-01-04 07:00:27

by Xiaoming Ni

Subject: ping //Re: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters.

ping


On 2020/12/24 15:42, 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 <[email protected]>
> ---
> 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;
>
>

2021-01-06 23:48:51

by Kees Cook

Subject: Re: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters.

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 <[email protected]>
> ---
> 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

2021-01-07 06:16:42

by Xiaoming Ni

Subject: Re: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters.

On 2021/1/7 7:46, Kees Cook wrote:
> 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 <[email protected]>
>> ---
>> 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;
> }
>
Yes, it's better to add log output.
Thank you for your review.
Do I need to send V2 patch based on review comments?

Thanks
Xiaoming Ni

2021-01-07 21:11:49

by Kees Cook

Subject: Re: [PATCH] proc_sysclt: fix oops caused by incorrect command parameters.

On Thu, Jan 07, 2021 at 02:14:18PM +0800, Xiaoming Ni wrote:
> On 2021/1/7 7:46, Kees Cook wrote:
> > subject typo: "sysclt" -> "sysctl"
> >
> > On Thu, Dec 24, 2020 at 03:42:56PM +0800, Xiaoming Ni wrote:
> > > [...]
> > > + 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;
> > }
> >
> Yes, it's better to add log output.
> Thank you for your review.
> Do I need to send V2 patch based on review comments?

Yes please. :)

--
Kees Cook