From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: + z3fold-fix-use-after-free-when-freeing-handles.patch added to -mm tree Date: Wed, 20 May 2020 17:47:04 -0700 Message-ID: <20200521004704.PNIP1YkNw%akpm@linux-foundation.org> References: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:35266 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726819AbgEUArF (ORCPT ); Wed, 20 May 2020 20:47:05 -0400 In-Reply-To: <20200513175005.1f4839360c18c0238df292d1@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: cai@lca.pw, mm-commits@vger.kernel.org, shentino@gmail.com, stable@vger.kernel.org, uladzislau.rezki@sony.com, vitaly.wool@konsulko.com The patch titled Subject: z3fold: fix use-after-free when freeing handles has been added to the -mm tree. Its filename is z3fold-fix-use-after-free-when-freeing-handles.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/z3fold-fix-use-after-free-when-freeing-handles.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/z3fold-fix-use-after-free-when-freeing-handles.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Uladzislau Rezki Subject: z3fold: fix use-after-free when freeing handles 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. Link: http://lkml.kernel.org/r/20200520082100.28876-1-vitaly.wool@konsulko.com Signed-off-by: Uladzislau Rezki Signed-off-by: Vitaly Wool Cc: Qian Cai Cc: Raymond Jennings Cc: Signed-off-by: Andrew Morton --- mm/z3fold.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) --- a/mm/z3fold.c~z3fold-fix-use-after-free-when-freeing-handles +++ a/mm/z3fold.c @@ -318,16 +318,16 @@ static inline void free_handle(unsigned 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 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 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); _ Patches currently in -mm which might be from uladzislau.rezki@sony.com are z3fold-fix-use-after-free-when-freeing-handles.patch