* [PATCH] z3fold: fix use-after-free when freeing handles
@ 2020-05-20 8:21 vitaly.wool
2020-05-21 0:46 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: vitaly.wool @ 2020-05-20 8:21 UTC (permalink / raw)
To: linux-mm; +Cc: stable, cai, shentino, akpm, Uladzislau Rezki, Vitaly Wool
From: Uladzislau Rezki <uladzislau.rezki@sony.com>
free_handle() for a foreign handle may race with inter-page
compaction, what can lead to memory corruption. To avoid that,
take write lock not read lock in free_handle to be synchronized
with __release_z3fold_page().
For example KASAN can detect it:
[ 33.723357] ==================================================================
[ 33.723401] BUG: KASAN: use-after-free in LZ4_decompress_safe+0x2c4/0x3b8
[ 33.723418] Read of size 1 at addr ffffffc976695ca3 by task GoogleApiHandle/4121
[ 33.723428]
[ 33.723449] CPU: 0 PID: 4121 Comm: GoogleApiHandle Tainted: P S OE 4.19.81-perf+ #162
[ 33.723461] Hardware name: Sony Mobile Communications. PDX-203(KONA) (DT)
[ 33.723473] Call trace:
[ 33.723495] dump_backtrace+0x0/0x288
[ 33.723512] show_stack+0x14/0x20
[ 33.723533] dump_stack+0xe4/0x124
[ 33.723551] print_address_description+0x80/0x2e0
[ 33.723566] kasan_report+0x268/0x2d0
[ 33.723584] __asan_load1+0x4c/0x58
[ 33.723601] LZ4_decompress_safe+0x2c4/0x3b8
[ 33.723619] lz4_decompress_crypto+0x3c/0x70
[ 33.723636] crypto_decompress+0x58/0x70
[ 33.723656] zcomp_decompress+0xd4/0x120
...
Apart from that, initialize zhdr->mapped_count in init_z3fold_page()
and remove "newpage" variable because it is not used anywhere.
Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
---
mm/z3fold.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 42f31c4b53ad..8c3bb5e508b8 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -318,16 +318,16 @@ static inline void free_handle(unsigned long handle)
slots = handle_to_slots(handle);
write_lock(&slots->lock);
*(unsigned long *)handle = 0;
- write_unlock(&slots->lock);
- if (zhdr->slots == slots)
+ if (zhdr->slots == slots) {
+ write_unlock(&slots->lock);
return; /* simple case, nothing else to do */
+ }
/* we are freeing a foreign handle if we are here */
zhdr->foreign_handles--;
is_free = true;
- read_lock(&slots->lock);
if (!test_bit(HANDLES_ORPHANED, &slots->pool)) {
- read_unlock(&slots->lock);
+ write_unlock(&slots->lock);
return;
}
for (i = 0; i <= BUDDY_MASK; i++) {
@@ -336,7 +336,7 @@ static inline void free_handle(unsigned long handle)
break;
}
}
- read_unlock(&slots->lock);
+ write_unlock(&slots->lock);
if (is_free) {
struct z3fold_pool *pool = slots_to_pool(slots);
@@ -422,6 +422,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
zhdr->start_middle = 0;
zhdr->cpu = -1;
zhdr->foreign_handles = 0;
+ zhdr->mapped_count = 0;
zhdr->slots = slots;
zhdr->pool = pool;
INIT_LIST_HEAD(&zhdr->buddy);
--
2.20.1
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] z3fold: fix use-after-free when freeing handles
2020-05-20 8:21 [PATCH] z3fold: fix use-after-free when freeing handles vitaly.wool
@ 2020-05-21 0:46 ` Andrew Morton
2020-05-21 8:04 ` Vitaly Wool
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2020-05-21 0:46 UTC (permalink / raw)
To: vitaly.wool; +Cc: linux-mm, stable, cai, shentino, Uladzislau Rezki
On Wed, 20 May 2020 11:21:00 +0300 vitaly.wool@konsulko.com wrote:
> From: Uladzislau Rezki <uladzislau.rezki@sony.com>
>
> free_handle() for a foreign handle may race with inter-page
> compaction, what can lead to memory corruption. To avoid that,
> take write lock not read lock in free_handle to be synchronized
> with __release_z3fold_page().
>
> For example KASAN can detect it:
>
> [ 33.723357] ==================================================================
> [ 33.723401] BUG: KASAN: use-after-free in LZ4_decompress_safe+0x2c4/0x3b8
> [ 33.723418] Read of size 1 at addr ffffffc976695ca3 by task GoogleApiHandle/4121
> [ 33.723428]
> [ 33.723449] CPU: 0 PID: 4121 Comm: GoogleApiHandle Tainted: P S OE 4.19.81-perf+ #162
> [ 33.723461] Hardware name: Sony Mobile Communications. PDX-203(KONA) (DT)
> [ 33.723473] Call trace:
> [ 33.723495] dump_backtrace+0x0/0x288
> [ 33.723512] show_stack+0x14/0x20
> [ 33.723533] dump_stack+0xe4/0x124
> [ 33.723551] print_address_description+0x80/0x2e0
> [ 33.723566] kasan_report+0x268/0x2d0
> [ 33.723584] __asan_load1+0x4c/0x58
> [ 33.723601] LZ4_decompress_safe+0x2c4/0x3b8
> [ 33.723619] lz4_decompress_crypto+0x3c/0x70
> [ 33.723636] crypto_decompress+0x58/0x70
> [ 33.723656] zcomp_decompress+0xd4/0x120
> ...
>
> Apart from that, initialize zhdr->mapped_count in init_z3fold_page()
> and remove "newpage" variable because it is not used anywhere.
>
> Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
I assume that a cc:stable is appropriate here?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] z3fold: fix use-after-free when freeing handles
2020-05-21 0:46 ` Andrew Morton
@ 2020-05-21 8:04 ` Vitaly Wool
0 siblings, 0 replies; 3+ messages in thread
From: Vitaly Wool @ 2020-05-21 8:04 UTC (permalink / raw)
To: Andrew Morton
Cc: Linux-MM, stable, Qian Cai, Raymond Jennings, Uladzislau Rezki
On Thu, May 21, 2020 at 2:46 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 20 May 2020 11:21:00 +0300 vitaly.wool@konsulko.com wrote:
>
> > From: Uladzislau Rezki <uladzislau.rezki@sony.com>
> >
> > free_handle() for a foreign handle may race with inter-page
> > compaction, what can lead to memory corruption. To avoid that,
> > take write lock not read lock in free_handle to be synchronized
> > with __release_z3fold_page().
> >
> > For example KASAN can detect it:
> >
> > [ 33.723357] ==================================================================
> > [ 33.723401] BUG: KASAN: use-after-free in LZ4_decompress_safe+0x2c4/0x3b8
> > [ 33.723418] Read of size 1 at addr ffffffc976695ca3 by task GoogleApiHandle/4121
> > [ 33.723428]
> > [ 33.723449] CPU: 0 PID: 4121 Comm: GoogleApiHandle Tainted: P S OE 4.19.81-perf+ #162
> > [ 33.723461] Hardware name: Sony Mobile Communications. PDX-203(KONA) (DT)
> > [ 33.723473] Call trace:
> > [ 33.723495] dump_backtrace+0x0/0x288
> > [ 33.723512] show_stack+0x14/0x20
> > [ 33.723533] dump_stack+0xe4/0x124
> > [ 33.723551] print_address_description+0x80/0x2e0
> > [ 33.723566] kasan_report+0x268/0x2d0
> > [ 33.723584] __asan_load1+0x4c/0x58
> > [ 33.723601] LZ4_decompress_safe+0x2c4/0x3b8
> > [ 33.723619] lz4_decompress_crypto+0x3c/0x70
> > [ 33.723636] crypto_decompress+0x58/0x70
> > [ 33.723656] zcomp_decompress+0xd4/0x120
> > ...
> >
> > Apart from that, initialize zhdr->mapped_count in init_z3fold_page()
> > and remove "newpage" variable because it is not used anywhere.
> >
> > Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
> > Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
>
> I assume that a cc:stable is appropriate here?
Absolutely. stable was in fact in CC: but it didn't reflect in the
patch for some reason. Thanks!
~Vitaly
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-05-20 8:21 [PATCH] z3fold: fix use-after-free when freeing handles vitaly.wool
2020-05-21 0:46 ` Andrew Morton
2020-05-21 8:04 ` Vitaly Wool
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