Messages in this thread | | | Subject | Re: [PATCH v2] proc_sysctl: fix oops caused by incorrect command parameters. | From | Xiaoming Ni <> | Date | Fri, 8 Jan 2021 18:01:52 +0800 |
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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 <nixiaoming@huawei.com> > > 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/20201224074256.117413-1-nixiaoming@huawei.com/ >> --------- >> --- >> 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
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