* Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > On Sat, Mar 24, 2018 at 9:29 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > > > * Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > > >> The krealloc function checks where the same buffer was reused or a new one > >> allocated by comparing kernel pointers. KHWASAN changes memory tag on the > >> krealloc'ed chunk of memory and therefore also changes the pointer tag of > >> the returned pointer. Therefore we need to perform comparison on untagged > >> (with tags reset) pointers to check whether it's the same memory region or > >> not. > >> > >> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > >> --- > >> mm/slab_common.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/mm/slab_common.c b/mm/slab_common.c > >> index a33e61315ca6..5911f2194cf7 100644 > >> --- a/mm/slab_common.c > >> +++ b/mm/slab_common.c > >> @@ -1494,7 +1494,7 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags) > >> } > >> > >> ret = __do_krealloc(p, new_size, flags); > >> - if (ret && p != ret) > >> + if (ret && khwasan_reset_tag(p) != khwasan_reset_tag(ret)) > >> kfree(p); > > > > Small nit: > > > > If 'reset' here means an all zeroes tag (upper byte) then khwasan_clear_tag() > > might be a slightly easier to read primitive? > > 'Reset' means to set the upper byte to the value that is native for > kernel pointers, and that is 0xFF. So it sets the tag to all ones, not > all zeroes. I can still rename it to khwasan_clear_tag(), if you think > that makes sense in this case as well. Ok, if it's not 0 then I agree that 'reset' is the better name. 'clear' would in fact be actively confusing. Thanks, Ingo
