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uma: trash memory when ctor/dtor supplied too

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On INVARIANTS kernels, UMA has a use-after-free detection mechanism.
This mechanism previously required that all of the ctor/dtor/uminit/fini
arguments to uma_zcreate() be NULL in order to function.  Now, it only
requires that uminit and fini be NULL; now, the trash ctor and dtor will
be called in addition to any supplied ctor or dtor.

Also do a little refactoring for readability of the resulting logic.

This enables use-after-free detection for more zones, and will allow for
simplification of some callers that worked around the previous
restriction (see kern_mbuf.c).

Reviewed by:	jeff, markj
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D20722
This commit is contained in:
Ryan Libby 2019-11-27 19:49:55 +00:00
parent 645f3a1cd1
commit ca293436d1
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=355137
2 changed files with 48 additions and 46 deletions
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93
sys/vm/uma_core.c
View File

@ -1869,6 +1869,11 @@ zone_ctor(void *mem, int size, void *udata, int flags)
for (i = 0; i < vm_ndomains; i++)
TAILQ_INIT(&zone->uz_domain[i].uzd_buckets);
#ifdef INVARIANTS
if (arg->uminit == trash_init && arg->fini == trash_fini)
zone->uz_flags |= UMA_ZFLAG_TRASH;
#endif
/*
* This is a pure cache zone, no kegs.
*/
@ -2302,14 +2307,17 @@ uma_zcreate(const char *name, size_t size, uma_ctor ctor, uma_dtor dtor,
args.fini = fini;
#ifdef INVARIANTS
/*
* If a zone is being created with an empty constructor and
* destructor, pass UMA constructor/destructor which checks for
* memory use after free.
* Inject procedures which check for memory use after free if we are
* allowed to scramble the memory while it is not allocated. This
* requires that: UMA is actually able to access the memory, no init
* or fini procedures, no dependency on the initial value of the
* memory, and no (legitimate) use of the memory after free. Note,
* the ctor and dtor do not need to be empty.
*
* XXX UMA_ZONE_OFFPAGE.
*/
if ((!(flags & (UMA_ZONE_ZINIT | UMA_ZONE_NOFREE))) &&
ctor == NULL && dtor == NULL && uminit == NULL && fini == NULL) {
args.ctor = trash_ctor;
args.dtor = trash_dtor;
uminit == NULL && fini == NULL) {
args.uminit = trash_init;
args.fini = trash_fini;
}
@ -2462,15 +2470,14 @@ static void *
item_ctor(uma_zone_t zone, void *udata, int flags, void *item)
{
#ifdef INVARIANTS
int skipdbg;
bool skipdbg;
skipdbg = uma_dbg_zskip(zone, item);
if (zone->uz_ctor != NULL &&
(!skipdbg || zone->uz_ctor != trash_ctor ||
zone->uz_dtor != trash_dtor) &&
#else
if (__predict_false(zone->uz_ctor != NULL) &&
if (!skipdbg && (zone->uz_flags & UMA_ZFLAG_TRASH) != 0 &&
zone->uz_ctor != trash_ctor)
trash_ctor(item, zone->uz_size, udata, flags);
#endif
if (__predict_false(zone->uz_ctor != NULL) &&
zone->uz_ctor(item, zone->uz_size, udata, flags) != 0) {
counter_u64_add(zone->uz_fails, 1);
zone_free_item(zone, item, udata, SKIP_DTOR | SKIP_CNT);
@ -2486,6 +2493,31 @@ item_ctor(uma_zone_t zone, void *udata, int flags, void *item)
return (item);
}
static inline void
item_dtor(uma_zone_t zone, void *item, void *udata, enum zfreeskip skip)
{
#ifdef INVARIANTS
bool skipdbg;
skipdbg = uma_dbg_zskip(zone, item);
if (skip == SKIP_NONE && !skipdbg) {
if ((zone->uz_flags & UMA_ZONE_MALLOC) != 0)
uma_dbg_free(zone, udata, item);
else
uma_dbg_free(zone, NULL, item);
}
#endif
if (skip < SKIP_DTOR) {
if (zone->uz_dtor != NULL)
zone->uz_dtor(item, zone->uz_size, udata);
#ifdef INVARIANTS
if (!skipdbg && (zone->uz_flags & UMA_ZFLAG_TRASH) != 0 &&
zone->uz_dtor != trash_dtor)
trash_dtor(item, zone->uz_size, udata);
#endif
}
}
/* See uma.h */
void *
uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
@ -2523,6 +2555,7 @@ uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
if (zone->uz_ctor != NULL &&
zone->uz_ctor(item, zone->uz_size, udata,
flags) != 0) {
counter_u64_add(zone->uz_fails, 1);
zone->uz_fini(item, zone->uz_size);
return (NULL);
}
@ -3131,9 +3164,6 @@ uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
int itemdomain;
#endif
bool lockfail;
#ifdef INVARIANTS
bool skipdbg;
#endif
/* Enable entropy collection for RANDOM_ENABLE_UMA kernel option */
random_harvest_fast_uma(&zone, sizeof(zone), RANDOM_UMA);
@ -3157,20 +3187,7 @@ uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
return;
}
#endif
#ifdef INVARIANTS
skipdbg = uma_dbg_zskip(zone, item);
if (skipdbg == false) {
if (zone->uz_flags & UMA_ZONE_MALLOC)
uma_dbg_free(zone, udata, item);
else
uma_dbg_free(zone, NULL, item);
}
if (zone->uz_dtor != NULL && (!skipdbg ||
zone->uz_dtor != trash_dtor || zone->uz_ctor != trash_ctor))
#else
if (zone->uz_dtor != NULL)
#endif
zone->uz_dtor(item, zone->uz_size, udata);
item_dtor(zone, item, udata, SKIP_NONE);
/*
* The race here is acceptable. If we miss it we'll just have to wait
@ -3459,24 +3476,8 @@ zone_release(uma_zone_t zone, void **bucket, int cnt)
static void
zone_free_item(uma_zone_t zone, void *item, void *udata, enum zfreeskip skip)
{
#ifdef INVARIANTS
bool skipdbg;
skipdbg = uma_dbg_zskip(zone, item);
if (skip == SKIP_NONE && !skipdbg) {
if (zone->uz_flags & UMA_ZONE_MALLOC)
uma_dbg_free(zone, udata, item);
else
uma_dbg_free(zone, NULL, item);
}
if (skip < SKIP_DTOR && zone->uz_dtor != NULL &&
(!skipdbg || zone->uz_dtor != trash_dtor ||
zone->uz_ctor != trash_ctor))
#else
if (skip < SKIP_DTOR && zone->uz_dtor != NULL)
#endif
zone->uz_dtor(item, zone->uz_size, udata);
item_dtor(zone, item, udata, skip);
if (skip < SKIP_FINI && zone->uz_fini)
zone->uz_fini(item, zone->uz_size);

1
sys/vm/uma_int.h
View File

@ -389,6 +389,7 @@ struct uma_zone {
#define UMA_ZFLAG_RECLAIMING 0x08000000 /* Running zone_reclaim(). */
#define UMA_ZFLAG_BUCKET 0x10000000 /* Bucket zone. */
#define UMA_ZFLAG_INTERNAL 0x20000000 /* No offpage no PCPU. */
#define UMA_ZFLAG_TRASH 0x40000000 /* Add trash ctor/dtor. */
#define UMA_ZFLAG_CACHEONLY 0x80000000 /* Don't ask VM for buckets. */
#define UMA_ZFLAG_INHERIT \