From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+f7b556d1766502a69d85071d2ff08bd87be53d0f@syzkaller.appspotmail.com, Eric Biggers , Tejun Heo Subject: [PATCH 3.18 05/93] libata: remove WARN() for DMA or PIO command without data Date: Fri, 6 Apr 2018 15:22:34 +0200 Message-Id: <20180406084225.201399322@linuxfoundation.org> In-Reply-To: <20180406084224.918716300@linuxfoundation.org> References: <20180406084224.918716300@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 9173e5e80729c8434b8d27531527c5245f4a5594 upstream. 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 Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- drivers/ata/libata-core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -5109,8 +5109,7 @@ void ata_qc_issue(struct ata_queued_cmd * 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) &&