From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: [PATCH] libata: remove WARN() for DMA or PIO command without data Date: Sat, 3 Feb 2018 20:33:27 -0800 Message-ID: <20180204043327.16760-1-ebiggers3@gmail.com> References: <001a11425956f5f3d0055c82f08d@google.com> Return-path: Received: from mail-pf0-f196.google.com ([209.85.192.196]:38498 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbeBDEdp (ORCPT ); Sat, 3 Feb 2018 23:33:45 -0500 In-Reply-To: <001a11425956f5f3d0055c82f08d@google.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-ide@vger.kernel.org, Tejun Heo Cc: linux-scsi@vger.kernel.org, syzkaller-bugs@googlegroups.com, Eric Biggers From: Eric Biggers syzkaller hit a WARN() in ata_qc_issue() when writing to /dev/sg0. This happened because it issued a READ_6 command with no data buffer. Just remove the WARN(), as it doesn't appear indicate a kernel bug. The expected behavior is to fail the command, which the code does. Here's a reproducer that works in QEMU when /dev/sg0 refers to a disk of the default type ("82371SB PIIX3 IDE"): #include #include int main() { char buf[42] = { [36] = 0x8 /* READ_6 */ }; write(open("/dev/sg0", O_RDWR), buf, sizeof(buf)); } Fixes: f92a26365a72 ("libata: change ATA_QCFLAG_DMAMAP semantics") Reported-by: syzbot+f7b556d1766502a69d85071d2ff08bd87be53d0f@syzkaller.appspotmail.com Cc: # v2.6.25+ Signed-off-by: Eric Biggers --- drivers/ata/libata-core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 3c09122bf0382..61b09968d0326 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -5401,8 +5401,7 @@ void ata_qc_issue(struct ata_queued_cmd *qc) * We guarantee to LLDs that they will have at least one * non-zero sg if the command is a data command. */ - if (WARN_ON_ONCE(ata_is_data(prot) && - (!qc->sg || !qc->n_elem || !qc->nbytes))) + if (ata_is_data(prot) && (!qc->sg || !qc->n_elem || !qc->nbytes)) goto sys_err; if (ata_is_dma(prot) || (ata_is_pio(prot) && -- 2.16.1