Commit e18086d6 authored by Mark Lord's avatar Mark Lord Committed by Jeff Garzik

[libata] More robust parsing for IDENTIFY DEVICE multi_count field

Make libata more robust when parsing the multi_count
field from a drive's identify data.  This prevents us from
attempting to use dubious multi_count values ad infinitum.

Reset dev->multi_count to zero and reprobe it each time
through this routine, as it can change on device reset.

Also ensure that the reported "maximum" value is valid
and is a power of two, and that the reported "count" value
is valid and also a power of two.  And that the "count"
value is not greater than the "maximum" value.
Signed-off-by: default avatarMark Lord <>
Signed-off-by: default avatarJeff Garzik <>
parent 000b344f
......@@ -57,6 +57,7 @@
#include <linux/scatterlist.h>
#include <linux/io.h>
#include <linux/async.h>
#include <linux/log2.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
......@@ -2389,6 +2390,7 @@ int ata_dev_configure(struct ata_device *dev)
dev->cylinders = 0;
dev->heads = 0;
dev->sectors = 0;
dev->multi_count = 0;
* common ATA, ATAPI feature tests
......@@ -2426,8 +2428,15 @@ int ata_dev_configure(struct ata_device *dev)
dev->n_sectors = ata_id_n_sectors(id);
if (dev->id[59] & 0x100)
dev->multi_count = dev->id[59] & 0xff;
/* get current R/W Multiple count setting */
if ((dev->id[47] >> 8) == 0x80 && (dev->id[59] & 0x100)) {
unsigned int max = dev->id[47] & 0xff;
unsigned int cnt = dev->id[59] & 0xff;
/* only recognize/allow powers of two here */
if (is_power_of_2(max) && is_power_of_2(cnt))
if (cnt <= max)
dev->multi_count = cnt;
if (ata_id_has_lba(id)) {
const char *lba_desc;
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