Re: [Crash-utility] [PATCH] Fix for "kmem <addr>" for kernels configured with CONFIG_SLUB and SLAB_RED_ZONE.
----- Original Message -----
OK, I understand. Let me work on a new "set redzone on/off" environment
variable that can be toggled on-and-off during runtime.
But I believe I see a problem in do_slab_slub(). When it is checking for free
objects to display as FREE / [ALLOCATED], it will never find it in 4.6+ kernels
with a red_left_pad. Note below, when it checks whether (p == q), the "q"
address
is the "shifted" address seen by the kmalloc() caller, and will never match
the
base object address "p", so "is_free" never gets set:
for (p = vaddr; p < vaddr + objects * si->size; p += si->size) {
hq_open();
is_free = FALSE;
/* Search an object on both of freelist and cpu_freelist */
ulong lists[] = { freelist, cpu_freelist, };
for (i = 0; i < sizeof(lists) / sizeof(lists[0]); i++) {
for (is_free = 0, q = lists[i]; q;
q = get_freepointer(si, (void *)q)) {
if (q == BADADDR) {
hq_close();
return FALSE;
}
if (q & PAGE_MAPPING_ANON)
break;
=== never can match ===> if (p == q) {
is_free = TRUE;
goto found_object;
}
if (!hq_enter(q)) {
hq_close();
error(INFO, "%s: slab: %lx duplicate
freelist object: %lx\n",
si->curname, si->slab, q);
return FALSE;
}
}
}
found_object:
...
Do you agree?
Ah -- I see that your first patch modified vaddr *before* the code segment
above. That would work in the case where the adjusted red-zone address
is used. But in order to handle both cases, the patch will need to be
adjusted for when the base address is used unmodified.
Dave