4.9-stable review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
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 <fcntl.h> #include <unistd.h>
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: stable@vger.kernel.org # v2.6.25+ Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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 @@ -5265,8 +5265,7 @@ 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) &&