This queue flag will let unprivileged users send any SG_IO command to the
device, without any filtering. This makes it possible to run a program
where you want to access the full range of SCSI commands, while still
running as confined as possible. With this patch, such a program will
not need the CAP_SYS_RAWIO capability anymore, and will also not be
able to send SCSI commands to a partition (which would affect the full
disk).
Cc: linux-scsi@xxxxxxxxxxxxxxx
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Ric Wheeler <rwheeler@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
v2->v3: change bitmap filter to boolean
block/blk-sysfs.c | 32 ++++++++++++++++++++++++++++++++
block/scsi_ioctl.c | 2 +-
include/linux/blkdev.h | 3 +++
3 files changed, 36 insertions(+), 1 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index ce62046..935d10a 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -215,6 +215,31 @@ static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
return queue_var_show(max_hw_sectors_kb, (page));
}
+static ssize_t
+queue_show_unpriv_sgio(struct request_queue *q, char *page)
+{
+ int bit;
+ bit = test_bit(QUEUE_FLAG_UNPRIV_SGIO, &q->queue_flags);
+ return queue_var_show(bit, page);
+}
+static ssize_t
+queue_store_unpriv_sgio(struct request_queue *q, const char *page, size_t count)
+{
+ unsigned long val;
+ ssize_t ret;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ ret = queue_var_store(&val, page, count);
+ spin_lock_irq(q->queue_lock);
+ if (val)
+ queue_flag_set(QUEUE_FLAG_UNPRIV_SGIO, q);
+ else
+ queue_flag_clear(QUEUE_FLAG_UNPRIV_SGIO, q);
+ spin_unlock_irq(q->queue_lock);
+ return ret;
+}
#define QUEUE_SYSFS_BIT_FNS(name, flag, neg) \
static ssize_t \
queue_show_##name(struct request_queue *q, char *page) \
@@ -403,6 +428,12 @@ static struct queue_sysfs_entry queue_nonrot_entry = {
.store = queue_store_nonrot,
};
+static struct queue_sysfs_entry queue_unpriv_sgio_entry = {
+ .attr = {.name = "unpriv_sgio", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_show_unpriv_sgio,
+ .store = queue_store_unpriv_sgio,
+};
+
static struct queue_sysfs_entry queue_nomerges_entry = {
.attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
.show = queue_nomerges_show,
@@ -445,6 +476,7 @@ static struct attribute *default_attrs[] = {
&queue_discard_max_entry.attr,
&queue_discard_zeroes_data_entry.attr,
&queue_write_same_max_entry.attr,
+ &queue_unpriv_sgio_entry.attr,
&queue_nonrot_entry.attr,
&queue_nomerges_entry.attr,
&queue_rq_affinity_entry.attr,
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index a737562..1a999d6 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -202,7 +202,7 @@ int blk_verify_command(struct request_queue *q,
struct blk_cmd_filter *filter = &blk_default_cmd_filter;
/* root can do any command. */
- if (capable(CAP_SYS_RAWIO))
+ if (capable(CAP_SYS_RAWIO) || blk_queue_unpriv_sgio(q))
return 0;
/* if there's no filter set, assume we're filtering everything out */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 69a5e55..169a883 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -452,6 +452,7 @@ struct request_queue {
#define QUEUE_FLAG_ADD_RANDOM 16 /* Contributes to random pool */
#define QUEUE_FLAG_SECDISCARD 17 /* supports SECDISCARD */
#define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */
+#define QUEUE_FLAG_UNPRIV_SGIO 19 /* SG_IO free for unprivileged users */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -526,6 +527,8 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_noxmerges(q) \
test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)
+#define blk_queue_unpriv_sgio(q) \
+ test_bit(QUEUE_FLAG_UNPRIV_SGIO, &(q)->queue_flags)
#define blk_queue_nonrot(q) test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
#define blk_queue_io_stat(q) test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
#define blk_queue_add_random(q) test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
--
1.7.4.1
--
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