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Narrow bounds on kernel malloc allocations. #2261

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Narrow bounds on kernel malloc allocations. #2261

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fb06d9c
uma: Add CHERI-specific uma_zgrow_bounds interface function.
qwattash Dec 5, 2024
3b947dd
uma: Set bounds on slab_data().
qwattash Dec 5, 2024
1a51a23
malloc(9): Narrow bounds for UMA-backed kmalloc allocations.
RoundofThree Nov 19, 2024
d5d3140
malloc(9): Narrow bounds for malloc_large allocations.
RoundofThree Nov 20, 2024
c4e4776
uma: Do not expose uma_slab inline functions to userspace.
qwattash Nov 25, 2024
6d78732
uma: Mark missing support for pcpu and smr zones in uma_zgrow_bounds.
qwattash Dec 5, 2024
96f85c4
malloc(9): Zero less space in malloc_large with CHERI.
qwattash Dec 5, 2024
3328083
malloc(9): Zero less space in UMA-backed allocations with CHERI.
qwattash Dec 5, 2024
942484f
malloc(9): Zero padding space in realloc with CHERI.
qwattash Dec 5, 2024
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62 changes: 49 additions & 13 deletions sys/kern/kern_malloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,7 @@ dtrace_malloc_probe_func_t __read_mostly dtrace_malloc_probe;
#define MALLOC_DEBUG 1
#endif

#if defined(KASAN) || defined(DEBUG_REDZONE)
#if defined(KASAN) || defined(DEBUG_REDZONE) || defined(__CHERI_PURE_CAPABILITY__)
#define DEBUG_REDZONE_ARG_DEF , unsigned long osize
#define DEBUG_REDZONE_ARG , osize
#else
Expand Down Expand Up @@ -680,7 +680,7 @@ void *
int indx;
caddr_t va;
uma_zone_t zone;
#if defined(DEBUG_REDZONE) || defined(KASAN)
#if defined(DEBUG_REDZONE) || defined(KASAN) || defined(__CHERI_PURE_CAPABILITY__)
unsigned long osize = size;
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I admit a temptation to slap a __diagused on at least the local variables and make them unconditional.

#endif

Expand All @@ -696,6 +696,14 @@ void *
return (malloc_large(size, mtp, DOMAINSET_RR(), flags
DEBUG_REDZONE_ARG));

/*
* XXX-AM: Imply M_ZERO to ensure that non-representable padding
* space is zero-initialized.
*/
if (size != CHERI_REPRESENTABLE_LENGTH(size)) {
flags |= M_ZERO;
}

if (size & KMEM_ZMASK)
size = (size & ~KMEM_ZMASK) + KMEM_ZBASE;
indx = kmemsize[size >> KMEM_ZSHIFT];
Expand All @@ -722,10 +730,13 @@ void *
kasan_mark((void *)va, osize, size, KASAN_MALLOC_REDZONE);
#endif
#ifdef __CHERI_PURE_CAPABILITY__
KASSERT(cheri_getlen(va) <= CHERI_REPRESENTABLE_LENGTH(size),
("Invalid bounds: expected %zx found %zx",
(size_t)CHERI_REPRESENTABLE_LENGTH(size),
(size_t)cheri_getlen(va)));
/* Intentionally inexect bounds allow for non-representable sizes */
va = cheri_setbounds(va, osize);
KASSERT(cheri_gettag(va),
("Invalid malloc: %#p requested size %zx", va, osize));
KASSERT(cheri_getlen(va) == CHERI_REPRESENTABLE_LENGTH(osize),
("Invalid malloc: %#p expected length %zx", va,
(size_t)CHERI_REPRESENTABLE_LENGTH(osize)));
#endif
return ((void *) va);
}
Expand Down Expand Up @@ -765,7 +776,7 @@ malloc_domainset(size_t size, struct malloc_type *mtp, struct domainset *ds,
caddr_t va;
int domain;
int indx;
#if defined(KASAN) || defined(DEBUG_REDZONE)
#if defined(KASAN) || defined(DEBUG_REDZONE) || defined(__CHERI_PURE_CAPABILITY__)
unsigned long osize = size;
#endif

Expand All @@ -781,6 +792,11 @@ malloc_domainset(size_t size, struct malloc_type *mtp, struct domainset *ds,
return (malloc_large(size, mtp, DOMAINSET_RR(), flags
DEBUG_REDZONE_ARG));

/* XXX-AM: see malloc() */
if (size != CHERI_REPRESENTABLE_LENGTH(size)) {
flags |= M_ZERO;
}

vm_domainset_iter_policy_init(&di, ds, &domain, &flags);
do {
va = malloc_domain(&size, &indx, mtp, domain, flags);
Expand All @@ -803,6 +819,15 @@ malloc_domainset(size_t size, struct malloc_type *mtp, struct domainset *ds,
kmsan_mark(va, size, KMSAN_STATE_UNINIT);
kmsan_orig(va, size, KMSAN_TYPE_MALLOC, KMSAN_RET_ADDR);
}
#endif
#ifdef __CHERI_PURE_CAPABILITY__
/* Intentionally inexect bounds allow for non-representable sizes */
va = cheri_setbounds(va, osize);
KASSERT(cheri_gettag(va),
("Invalid malloc: %#p requested size %zx", va, osize));
KASSERT(cheri_getlen(va) == CHERI_REPRESENTABLE_LENGTH(osize),
("Invalid malloc: %#p expected length %zx", va,
(size_t)CHERI_REPRESENTABLE_LENGTH(osize)));
#endif
return (va);
}
Expand All @@ -821,7 +846,7 @@ void *
malloc_domainset_exec(size_t size, struct malloc_type *mtp, struct domainset *ds,
int flags)
{
#if defined(DEBUG_REDZONE) || defined(KASAN)
#if defined(DEBUG_REDZONE) || defined(KASAN) || defined(__CHERI_PURE_CAPABILITY__)
unsigned long osize = size;
#endif
#ifdef MALLOC_DEBUG
Expand Down Expand Up @@ -996,11 +1021,10 @@ _free(void *addr, struct malloc_type *mtp, bool dozero)
case __predict_true(SLAB_COOKIE_SLAB_PTR):
size = zone->uz_size;
#ifdef __CHERI_PURE_CAPABILITY__
if (__predict_false(cheri_getlen(addr) !=
CHERI_REPRESENTABLE_LENGTH(size)))
panic("Invalid bounds: expected %zx found %zx",
(size_t)CHERI_REPRESENTABLE_LENGTH(size),
cheri_getlen(addr));
addr = uma_zgrow_bounds(zone, addr);
KASSERT(cheri_getlen(addr) == size,
("vtozoneslab disagrees witht uma_zgrow_bounds: %zx != %zx",
cheri_getlen(addr), size));
#endif
#if defined(INVARIANTS) && !defined(KASAN)
free_save_type(addr, mtp, size);
Expand Down Expand Up @@ -1074,6 +1098,10 @@ realloc(void *addr, size_t size, struct malloc_type *mtp, int flags)
#endif
unsigned long alloc;
void *newaddr;
#ifdef __CHERI_PURE_CAPABILITY__
uma_keg_t keg;
int i;
#endif

KASSERT(mtp->ks_version == M_VERSION,
("realloc: bad malloc type version"));
Expand Down Expand Up @@ -1112,7 +1140,15 @@ realloc(void *addr, size_t size, struct malloc_type *mtp, int flags)
/* Get the size of the original block */
switch (GET_SLAB_COOKIE(slab)) {
case __predict_true(SLAB_COOKIE_SLAB_PTR):
#ifdef __CHERI_PURE_CAPABILITY__
alloc = zone->uz_size;
keg = zone->uz_keg;
i = slab_item_index(slab, keg, addr);
addr = slab_item(slab, keg, i);
addr = cheri_setboundsexact(addr, alloc);
#else
alloc = zone->uz_size;
#endif
break;
case SLAB_COOKIE_MALLOC_LARGE:
alloc = malloc_large_size(slab);
Expand Down
21 changes: 4 additions & 17 deletions sys/vm/uma_int.h
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Original file line number Diff line number Diff line change
Expand Up @@ -413,24 +413,11 @@ slab_tohashslab(uma_slab_t slab)
static inline void *
slab_data(uma_slab_t slab, uma_keg_t keg)
{
void *data;

if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) == 0) {
data = (void *)cheri_kern_setboundsexact(
(uintptr_t)slab - keg->uk_pgoff, keg->uk_pgoff);
#ifdef __CHERI_PURE_CAPABILITY__
KASSERT(cheri_gettag(data),
("Unrepresentable slab uk_pgoff %x", keg->uk_pgoff));
#endif
} else {
data = slab_tohashslab(slab)->uhs_data;
#ifdef __CHERI_PURE_CAPABILITY__
KASSERT(cheri_getlen(data) == keg->uk_ppera * PAGE_SIZE,
("Unexpected offpage slab capability: %#p, "
"expected %d pages", data, keg->uk_ppera));
#endif
}
return (data);
if ((keg->uk_flags & UMA_ZFLAG_OFFPAGE) == 0)
return ((void *)((uintptr_t)slab - keg->uk_pgoff));
else
return (slab_tohashslab(slab)->uhs_data);
}

static inline void *
Expand Down