[ 032/221] SCSI: prevent stack buffer overflow in host_reset

Greg Kroah-Hartman
2013-01-15T18:56:49Z

From: Sasha Levin <sasha.levin@oracle.com>

commit 072f19b4bea31cdd482d79f805413f2f9ac9e233 upstream.

store_host_reset() has tried to re-invent the wheel to compare sysfs strings.
Unfortunately it did so poorly and never bothered to check the input from
userspace before overwriting stack with it, so something simple as:

echo "WoopsieWoopsie" >
/sys/devices/pseudo_0/adapter0/host0/scsi_host/host0/host_reset

would result in:

[ 316.310101] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81f5bac7
[ 316.310101]
[ 316.320051] Pid: 6655, comm: sh Tainted: G W 3.7.0-rc5-next-20121114-sasha-00016-g5c9d68d-dirty #129
[ 316.320051] Call Trace:
[ 316.340058] pps pps0: PPS event at 1352918752.620355751
[ 316.340062] pps pps0: capture assert seq #303
[ 316.320051] [<ffffffff83b3856b>] panic+0xcd/0x1f4
[ 316.320051] [<ffffffff81f5bac7>] ? store_host_reset+0xd7/0x100
[ 316.320051] [<ffffffff8110b996>] __stack_chk_fail+0x16/0x20
[ 316.320051] [<ffffffff81f5bac7>] store_host_reset+0xd7/0x100
[ 316.320051] [<ffffffff81e55bb3>] dev_attr_store+0x13/0x30
[ 316.320051] [<ffffffff812f7db1>] sysfs_write_file+0x101/0x170
[ 316.320051] [<ffffffff8127acc8>] vfs_write+0xb8/0x180
[ 316.320051] [<ffffffff8127ae80>] sys_write+0x50/0xa0
[ 316.320051] [<ffffffff83c03418>] tracesys+0xe1/0xe6

Fix this by uninventing whatever was going on there and just use sysfs_streq.

Bug introduced by 29443691 ("[SCSI] scsi: Added support for adapter and
firmware reset").

[jejb: added necessary const to prevent compile warnings]
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/scsi/scsi_sysfs.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -247,11 +247,11 @@ show_shost_active_mode(struct device *de

static DEVICE_ATTR(active_mode, S_IRUGO | S_IWUSR, show_shost_active_mode, NULL);

-static int check_reset_type(char *str)
+static int check_reset_type(const char *str)
{
- if (strncmp(str, "adapter", 10) == 0)
+ if (sysfs_streq(str, "adapter"))
return SCSI_ADAPTER_RESET;
- else if (strncmp(str, "firmware", 10) == 0)
+ else if (sysfs_streq(str, "firmware"))
return SCSI_FIRMWARE_RESET;
else
return 0;
@@ -264,12 +264,9 @@ store_host_reset(struct device *dev, str
struct Scsi_Host *shost = class_to_shost(dev);
struct scsi_host_template *sht = shost->hostt;
int ret = -EINVAL;
- char str[10];
int type;

- sscanf(buf, "%s", str);
- type = check_reset_type(str);
-
+ type = check_reset_type(buf);
if (!type)
goto exit_store_host_reset;