Prevent use of uninitialized memory (originating from the stack frame of do_sysctl()) by verifying that the name array is filled with sufficient input data before comparing its specific entries with integer constants. Through timing measurement or analyzing the kernel debug logs, a user-mode program could potentially infer the results of comparisons against the uninitialized memory, and acquire some (very limited) information about the state of the kernel stack. The change also eliminates possible future warnings by tools such as KMSAN and other code checkers / instrumentations.
Showing the changes to kernel/sysctl_binary.c (1 of 1 file). Show all
Unified · Split
| @@ -1346,7 +1346,7 @@ static void deprecated_sysctl_warning(const int *name, int nlen) · 1345 unmodified lines | |||
| 1346 | * CTL_KERN/KERN_VERSION is used by older glibc and cannot | 1346 | * CTL_KERN/KERN_VERSION is used by older glibc and cannot |
| 1347 | * ever go away. | 1347 | * ever go away. |
| 1348 | */ | 1348 | */ |
| 1349 | if (name[0] == CTL_KERN && name[1] == KERN_VERSION) | 1349 | if (nlen >= 2 && name[0] == CTL_KERN && name[1] == KERN_VERSION) |
| 1350 | return; | 1350 | return; |
| 1351 | 1351 | ||
| 1352 | if (printk_ratelimit()) { | 1352 | if (printk_ratelimit()) { |