From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1520458851; cv=none; d=google.com; s=arc-20160816; b=S4tbqfZS9SE+oqqoSBa6xn0coZiVp+A5pR6EMpxOTg5aGW4FChxihDo2ipev93Jj+5 XwLz9RHtCy8lssZ0DtlEhl+qqzZxnyJhDrQYWMOd7pirXSrK3aDWK50DsZBsbWjs+URC U/aU6SM8Snd6tdB+oq5uYTI6f7MwuvCkMOsOIHNWA9JLTenye3xFHXTQd/b9i1OFcisH 37J0zFbstutBkONBoGssjQb1gV7/PsBCW3Ko4LPNdGgdZkfvCtGyn+PyObI3zEpQ//HU +xaPaeaIBD4veNb3k17BMUKNmyjKkxxH0GRbetoJO/43+k7pcu+5Spp4+hC9tLODZhTV phPA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from:dkim-signature :arc-authentication-results; bh=u4Vhm/eZ+riIyfjjPrRuoBA80Cv/bPWVvRfrRQPJIoM=; b=DGicvmjljgUFFwmBJ6VYNtXW7A5AYLVodgcWpjg7gVh4gr8ez7eNUZfcF98q3RuZSr 1YI2b5IE+W9+KSAf105MhC3V97xLwb1xE8BZc5FzTbjlbMvw2PS6UbKRN5MCYd7B1IJr fOKM+pfYTgRV9ZgztxueXO56KmzwyR57W23w6o9kxGzpNPSIbRKBv1wo/WxBhOqJ0fGN rKzXkqR/HMqiiF3EzwDugfPWsQKoWnToEv+bBIoM8kHFk+v3tkYS4Mq97VUXwyD80RcP 8boQH/IF0gtT7CleGj1F3eg8woBD2t8ZcmqSpc5F9gpAVqd4tpNFigo9q5HVSxQAOoXD kKmg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=mWuU5wTX; spf=pass (google.com: domain of paullawrence@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=paullawrence@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=mWuU5wTX; spf=pass (google.com: domain of paullawrence@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=paullawrence@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Google-Smtp-Source: AG47ELsA71G81u2ZRPt7I90IRiHMhSSdJ7eFVsdXj3ckZTd/ngxKyz4cxpwOmDNCkE7G4XOL4gZFbw== From: Paul Lawrence To: linux-kernel@vger.kernel.org Cc: Paul Lawrence , stable@vger.kernel.org, Ben Hutchings , Greg Kroah-Hartman , =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Martijn Coenen , devel@driverdev.osuosl.org Subject: [PATCH] staging: android: ashmem: Remove deadlock Date: Wed, 7 Mar 2018 13:40:30 -0800 Message-Id: <20180307214042.135109-1-paullawrence@google.com> X-Mailer: git-send-email 2.16.2.395.g2e18187dfd-goog X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594316660298021299?= X-GMAIL-MSGID: =?utf-8?q?1594316660298021299?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Regression introduced in commit ce8a3a9e76d0193e2e8d74a06d275b3c324ca652 ("staging: android: ashmem: Fix a race condition in pin ioctls") causing deadlock. No need to hold ashmem_mutex while copying from user Stacks are: ashmem_mmap+0x53/0x400 drivers/staging/android/ashmem.c:379 mmap_region+0x7dd/0xfd0 mm/mmap.c:1694 do_mmap+0x57b/0xbe0 mm/mmap.c:1473 and lock_acquire+0x12e/0x410 kernel/locking/lockdep.c:3756 __might_fault+0x14a/0x1d0 mm/memory.c:4014 copy_from_user arch/x86/include/asm/uaccess.h:705 [inline] ashmem_pin_unpin drivers/staging/android/ashmem.c:719 [inline] Signed-off-by: Paul Lawrence Cc: # 4.9.x Cc: # 4.4.x Cc: # 3.18.x: ce8a3a9e76d01 Cc: # 3.18.x Cc: Ben Hutchings --- drivers/staging/android/ashmem.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c index 6dbba5aff191..8c55706c2cfa 100644 --- a/drivers/staging/android/ashmem.c +++ b/drivers/staging/android/ashmem.c @@ -702,16 +702,14 @@ static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd, size_t pgstart, pgend; int ret = -EINVAL; + if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) + return -EFAULT; + mutex_lock(&ashmem_mutex); if (unlikely(!asma->file)) goto out_unlock; - if (unlikely(copy_from_user(&pin, p, sizeof(pin)))) { - ret = -EFAULT; - goto out_unlock; - } - /* per custom, you can pass zero for len to mean "everything onward" */ if (!pin.len) pin.len = PAGE_ALIGN(asma->size) - pin.offset; -- 2.16.2.395.g2e18187dfd-goog