From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v2.6.25+
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
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
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