From 9173e5e80729c8434b8d27531527c5245f4a5594 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sat, 3 Feb 2018 20:33:27 -0800 Subject: [PATCH] libata: remove WARN() for DMA or PIO command without data 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 --- 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 3c09122bf038..61b09968d032 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) &&