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@xxxxxxxxxx>
---------
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@xxxxxxxxxx/
---------
---
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
