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]>
---------
v2:
Added log output of the failure branch based on the review comments of Kees Cook.
v1: https://lore.kernel.org/lkml/[email protected]/
---------
---
fs/proc/proc_sysctl.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 317899222d7f..dc1a56515e86 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
loff_t pos = 0;
ssize_t wret;
+ if (!val) {
+ pr_err("Missing param value! Expected '%s=...value...'\n", param);
+ return 0;
+ }
+
if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
param += sizeof("sysctl") - 1;
--
2.27.0
On Fri 08-01-21 10:33:39, 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]>
Thanks for catching this!
> ---------
> v2:
> Added log output of the failure branch based on the review comments of Kees Cook.
> v1: https://lore.kernel.org/lkml/[email protected]/
> ---------
> ---
> fs/proc/proc_sysctl.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index 317899222d7f..dc1a56515e86 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
> loff_t pos = 0;
> ssize_t wret;
>
> + if (!val) {
> + pr_err("Missing param value! Expected '%s=...value...'\n", param);
> + return 0;
> + }
Shouldn't you return an error here? Also my understanding is that
parse_args is responsible for reporting the error.
> +
> if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
> param += sizeof("sysctl") - 1;
>
> --
> 2.27.0
--
Michal Hocko
SUSE Labs
On 2021/1/8 17:21, Michal Hocko wrote:
> On Fri 08-01-21 10:33:39, 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]>
>
> Thanks for catching this!
>
>> ---------
>> v2:
>> Added log output of the failure branch based on the review comments of Kees Cook.
>> v1: https://lore.kernel.org/lkml/[email protected]/
>> ---------
>> ---
>> fs/proc/proc_sysctl.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
>> index 317899222d7f..dc1a56515e86 100644
>> --- a/fs/proc/proc_sysctl.c
>> +++ b/fs/proc/proc_sysctl.c
>> @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
>> loff_t pos = 0;
>> ssize_t wret;
>>
>> + if (!val) {
>> + pr_err("Missing param value! Expected '%s=...value...'\n", param);
>> + return 0;
I may need to move the validation code for val to the end of the
validation code for param to prevent non-sysctl arguments from
triggering the current print.
Or delete the print and keep it silent for a little better performance.
Which is better?
>> + }
>
> Shouldn't you return an error here? Also my understanding is that
> parse_args is responsible for reporting the error.
>
All exception branches in process_sysctl_arg record logs and return 0.
Do I need to keep the same processing in the new branch?
>> +
>> if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
>> param += sizeof("sysctl") - 1;
>>
>> --
>> 2.27.0
>
Thanks
Xiaoming Ni
On Fri 08-01-21 18:01:52, Xiaoming Ni wrote:
> On 2021/1/8 17:21, Michal Hocko wrote:
> > On Fri 08-01-21 10:33:39, 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]>
> >
> > Thanks for catching this!
> >
> > > ---------
> > > v2:
> > > Added log output of the failure branch based on the review comments of Kees Cook.
> > > v1: https://lore.kernel.org/lkml/[email protected]/
> > > ---------
> > > ---
> > > fs/proc/proc_sysctl.c | 5 +++++
> > > 1 file changed, 5 insertions(+)
> > >
> > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> > > index 317899222d7f..dc1a56515e86 100644
> > > --- a/fs/proc/proc_sysctl.c
> > > +++ b/fs/proc/proc_sysctl.c
> > > @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
> > > loff_t pos = 0;
> > > ssize_t wret;
> > > + if (!val) {
> > > + pr_err("Missing param value! Expected '%s=...value...'\n", param);
> > > + return 0;
> I may need to move the validation code for val to the end of the validation
> code for param to prevent non-sysctl arguments from triggering the current
> print.
Why would that matter? A missing value is clearly a error path and it
should be reported.
> Or delete the print and keep it silent for a little better performance.
> Which is better?
I do not think there is a performance argument on the table. The generic
code is returning EINVAL on a missing value where it is needed. Sysctl
all require a value IIRC so EINVAL would be the right way to report
this and let the generic code to complain.
--
Michal Hocko
SUSE Labs
On Fri, Jan 08, 2021 at 12:47:18PM +0100, Michal Hocko wrote:
> On Fri 08-01-21 18:01:52, Xiaoming Ni wrote:
> > On 2021/1/8 17:21, Michal Hocko wrote:
> > > On Fri 08-01-21 10:33:39, 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]>
> > >
> > > Thanks for catching this!
> > >
> > > > ---------
> > > > v2:
> > > > Added log output of the failure branch based on the review comments of Kees Cook.
> > > > v1: https://lore.kernel.org/lkml/[email protected]/
> > > > ---------
> > > > ---
> > > > fs/proc/proc_sysctl.c | 5 +++++
> > > > 1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> > > > index 317899222d7f..dc1a56515e86 100644
> > > > --- a/fs/proc/proc_sysctl.c
> > > > +++ b/fs/proc/proc_sysctl.c
> > > > @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
> > > > loff_t pos = 0;
> > > > ssize_t wret;
> > > > + if (!val) {
> > > > + pr_err("Missing param value! Expected '%s=...value...'\n", param);
> > > > + return 0;
> > I may need to move the validation code for val to the end of the validation
> > code for param to prevent non-sysctl arguments from triggering the current
> > print.
>
> Why would that matter? A missing value is clearly a error path and it
> should be reported.
This test is in the correct place. I think it's just a question of the
return values.
> > Or delete the print and keep it silent for a little better performance.
> > Which is better?
>
> I do not think there is a performance argument on the table. The generic
> code is returning EINVAL on a missing value where it is needed. Sysctl
> all require a value IIRC so EINVAL would be the right way to report
> this and let the generic code to complain.
The reason the others do a "return 0" is because other error conditions
will end up double-reporting:
switch (ret) {
case 0:
continue;
case -ENOENT:
pr_err("%s: Unknown parameter `%s'\n", doing, param);
break;
case -ENOSPC:
pr_err("%s: `%s' too large for parameter `%s'\n",
doing, val ?: "", param);
break;
default:
pr_err("%s: `%s' invalid for parameter `%s'\n",
doing, val ?: "", param);
break;
}
Also note that where the sysctl parsing happens, it calls parse_args()
without checking return codes, so that doesn't matter either.
It's possible that doing this would be sufficient, though:
+ if (!val)
+ return -EINVAL;
Since that would hit the "default" error report which looks reasonable.
--
Kees Cook
On Fri 08-01-21 11:56:33, Kees Cook wrote:
> On Fri, Jan 08, 2021 at 12:47:18PM +0100, Michal Hocko wrote:
> > On Fri 08-01-21 18:01:52, Xiaoming Ni wrote:
> > > On 2021/1/8 17:21, Michal Hocko wrote:
> > > > On Fri 08-01-21 10:33:39, 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]>
> > > >
> > > > Thanks for catching this!
> > > >
> > > > > ---------
> > > > > v2:
> > > > > Added log output of the failure branch based on the review comments of Kees Cook.
> > > > > v1: https://lore.kernel.org/lkml/[email protected]/
> > > > > ---------
> > > > > ---
> > > > > fs/proc/proc_sysctl.c | 5 +++++
> > > > > 1 file changed, 5 insertions(+)
> > > > >
> > > > > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> > > > > index 317899222d7f..dc1a56515e86 100644
> > > > > --- a/fs/proc/proc_sysctl.c
> > > > > +++ b/fs/proc/proc_sysctl.c
> > > > > @@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char *val,
> > > > > loff_t pos = 0;
> > > > > ssize_t wret;
> > > > > + if (!val) {
> > > > > + pr_err("Missing param value! Expected '%s=...value...'\n", param);
> > > > > + return 0;
> > > I may need to move the validation code for val to the end of the validation
> > > code for param to prevent non-sysctl arguments from triggering the current
> > > print.
> >
> > Why would that matter? A missing value is clearly a error path and it
> > should be reported.
>
> This test is in the correct place. I think it's just a question of the
> return values.
I was probably not clear. The test for val is at the right place. I
would just expect -EINVAL and have the generic code to report.
--
Michal Hocko
SUSE Labs
On Fri, 8 Jan 2021 21:10:25 +0100 Michal Hocko <[email protected]> wrote:
> > > Why would that matter? A missing value is clearly a error path and it
> > > should be reported.
> >
> > This test is in the correct place. I think it's just a question of the
> > return values.
>
> I was probably not clear. The test for val is at the right place. I
> would just expect -EINVAL and have the generic code to report.
It does seem a bit screwy that process_sysctl_arg() returns zero in all
situations (parse_args() is set up to handle an error return from it).
But this patch is consistent with all the other error handling in
process_sysctl_arg().
On 2021/1/9 17:10, Andy Shevchenko wrote:
>
>
> On Friday, January 8, 2021, Xiaoming Ni <[email protected]
> <mailto:[email protected]>> 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:
>
>
> Can you drop redundant (not significant) lines from the log to avoid
> noisy commit message?
>
ok,
Thank you for your advice.
I will update it in v3 patch.
Thanks
Xiaoming Ni.
On 2021/1/9 9:50, Andrew Morton wrote:
> On Fri, 8 Jan 2021 21:10:25 +0100 Michal Hocko <[email protected]> wrote:
>
>>>> Why would that matter? A missing value is clearly a error path and it
>>>> should be reported.
>>>
>>> This test is in the correct place. I think it's just a question of the
>>> return values.
>>
>> I was probably not clear. The test for val is at the right place. I
>> would just expect -EINVAL and have the generic code to report.
>
> It does seem a bit screwy that process_sysctl_arg() returns zero in all
> situations (parse_args() is set up to handle an error return from it).
> But this patch is consistent with all the other error handling in
> process_sysctl_arg().
> .
>
Set the kernel startup parameter to "nosmp nokaslr hung_task_panic"
and test the startup logs of different patches.
patch1:
+++ b/fs/proc/proc_sysctl.c
@@ -1757,6 +1757,11 @@ static int process_sysctl_arg(char *param, char
*val,
loff_t pos = 0;
ssize_t wret;
+ if (!val) {
+ pr_err("Missing param value! Expected
'%s=...value...'\n", param);
+ return 0;
+ }
+
if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
param += sizeof("sysctl") - 1;
sysctl log for patch1:
Missing param value! Expected 'nosmp=...value...'
Missing param value! Expected 'nokaslr=...value...'
Missing param value! Expected 'hung_task_panic=...value...'
patch2:
+++ b/fs/proc/proc_sysctl.c
@@ -1756,6 +1756,8 @@ static int process_sysctl_arg(char *param, char *val,
int err;
loff_t pos = 0;
ssize_t wret;
+ if (!val)
+ return -EINVAL;
if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
param += sizeof("sysctl") - 1;
sysctl log for patch2:
Setting sysctl args: `' invalid for parameter `nosmp'
Setting sysctl args: `' invalid for parameter `nokaslr'
Setting sysctl args: `' invalid for parameter `hung_task_panic'
patch3:
+++ b/fs/proc/proc_sysctl.c
@@ -1770,6 +1770,9 @@ static int process_sysctl_arg(char *param, char *val,
return 0;
}
+ if (!val)
+ return -EINVAL;
+
/*
* To set sysctl options, we use a temporary mount of proc, look up the
* respective sys/ file and write to it. To avoid mounting it when no
sysctl log for patch3:
Setting sysctl args: `' invalid for parameter `hung_task_panic'
patch4:
+++ 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;
sysctl log for patch3:
no log
When process_sysctl_arg() is called, the param parameter may not be the
sysctl parameter.
Patch3 or patch4, which is better?
Thanks
Xiaoming Ni
On Mon 11-01-21 11:48:19, Xiaoming Ni wrote:
[...]
> patch3:
> +++ b/fs/proc/proc_sysctl.c
> @@ -1770,6 +1770,9 @@ static int process_sysctl_arg(char *param, char *val,
> return 0;
> }
>
> + if (!val)
> + return -EINVAL;
> +
> /*
> * To set sysctl options, we use a temporary mount of proc, look up the
> * respective sys/ file and write to it. To avoid mounting it when no
>
> sysctl log for patch3:
> Setting sysctl args: `' invalid for parameter `hung_task_panic'
[...]
> When process_sysctl_arg() is called, the param parameter may not be the
> sysctl parameter.
>
> Patch3 or patch4, which is better?
Patch3
--
Michal Hocko
SUSE Labs
On Mon, Jan 11, 2021 at 03:21:31PM +0100, Michal Hocko wrote:
> On Mon 11-01-21 11:48:19, Xiaoming Ni wrote:
> [...]
> > patch3:
> > +++ b/fs/proc/proc_sysctl.c
> > @@ -1770,6 +1770,9 @@ static int process_sysctl_arg(char *param, char *val,
> > return 0;
> > }
> >
> > + if (!val)
> > + return -EINVAL;
> > +
> > /*
> > * To set sysctl options, we use a temporary mount of proc, look up the
> > * respective sys/ file and write to it. To avoid mounting it when no
> >
> > sysctl log for patch3:
> > Setting sysctl args: `' invalid for parameter `hung_task_panic'
> [...]
> > When process_sysctl_arg() is called, the param parameter may not be the
> > sysctl parameter.
> >
> > Patch3 or patch4, which is better?
>
> Patch3
Oh, I see the issue here -- I thought we were only calling
process_sysctl_arg() with valid sysctl fields. It looks like we're not,
which means it should silently ignore everything that isn't a sysctl
field, and only return -EINVAL when it IS a sysctl but it lacks a value.
--
Kees Cook