On Mon, Sep 7, 2020 at 3:41 PM Marco Elver <elver@xxxxxxxxxx> wrote: > +config KFENCE_NUM_OBJECTS > + int "Number of guarded objects available" > + default 255 > + range 1 65535 > + help > + The number of guarded objects available. For each KFENCE object, 2 > + pages are required; with one containing the object and two adjacent > + ones used as guard pages. Hi Marco, Wonder if you tested build/boot with KFENCE_NUM_OBJECTS=65535? Can a compiler create such a large object? > +config KFENCE_FAULT_INJECTION > + int "Fault injection for stress testing" > + default 0 > + depends on EXPERT > + help > + The inverse probability with which to randomly protect KFENCE object > + pages, resulting in spurious use-after-frees. The main purpose of > + this option is to stress-test KFENCE with concurrent error reports > + and allocations/frees. A value of 0 disables fault injection. I would name this differently. "FAULT_INJECTION" is already taken for a different thing, so it's a bit confusing. KFENCE_DEBUG_SOMETHING may be a better name. It would also be good to make it very clear in the short description that this is for testing of KFENCE itself. When I configure syzbot I routinely can't figure out if various DEBUG configs detect user errors, or enable additional unit tests, or something else. Maybe it should depend on DEBUG_KERNEL as well? > +/* > + * Get the canary byte pattern for @addr. Use a pattern that varies based on the > + * lower 3 bits of the address, to detect memory corruptions with higher > + * probability, where similar constants are used. > + */ > +#define KFENCE_CANARY_PATTERN(addr) ((u8)0xaa ^ (u8)((unsigned long)addr & 0x7)) (addr) in macro body > + seq_con_printf(seq, > + "kfence-#%zd [0x" PTR_FMT "-0x" PTR_FMT PTR_FMT is only used in this file, should it be declared in report.c? Please post example reports somewhere. It's hard to figure out all details of the reporting/formatting.
