[PATCH 1/3] scsi: sg: protect accesses to 'reserved' page array
Tyler Hicks
tyhicks at canonical.com
Fri Sep 28 21:29:15 UTC 2018
From: Hannes Reinecke <hare at suse.de>
The 'reserved' page array is used as a short-cut for mapping data,
saving us to allocate pages per request. However, the 'reserved' array
is only capable of holding one request, so this patch introduces a mutex
for protect 'sg_fd' against concurrent accesses.
Signed-off-by: Hannes Reinecke <hare at suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Tested-by: Johannes Thumshirn <jthumshirn at suse.de>
Reviewed-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
CVE-2017-0794
(backported from commit 1bc0eb0446158cc76562176b80623aa119afee5b)
[tyhicks: Minor context changes]
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
drivers/scsi/sg.c | 53 +++++++++++++++++++++++++++++++----------------------
1 file changed, 31 insertions(+), 22 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 4fecbb164104..ee23298dd955 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -151,6 +151,7 @@ typedef struct sg_fd { /* holds the state of a file descriptor */
struct sg_device *parentdp; /* owning device */
wait_queue_head_t read_wait; /* queue read until command done */
rwlock_t rq_list_lock; /* protect access to list in req_arr */
+ struct mutex f_mutex; /* protect against changes in this fd */
int timeout; /* defaults to SG_DEFAULT_TIMEOUT */
int timeout_user; /* defaults to SG_DEFAULT_TIMEOUT_USER */
Sg_scatter_hold reserve; /* buffer held for this file descriptor */
@@ -164,6 +165,7 @@ typedef struct sg_fd { /* holds the state of a file descriptor */
char next_cmd_len; /* 0 -> automatic (def), >0 -> use on next write() */
char keep_orphan; /* 0 -> drop orphan (def), 1 -> keep for read() */
char mmap_called; /* 0 -> mmap() never called on this fd */
+ char res_in_use; /* 1 -> 'reserve' array in use */
struct kref f_ref;
struct execute_work ew;
} Sg_fd;
@@ -206,7 +208,6 @@ static void sg_remove_sfp(struct kref *);
static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id);
static Sg_request *sg_add_request(Sg_fd * sfp);
static int sg_remove_request(Sg_fd * sfp, Sg_request * srp);
-static int sg_res_in_use(Sg_fd * sfp);
static Sg_device *sg_get_dev(int dev);
static void sg_put_dev(Sg_device *sdp);
@@ -600,6 +601,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
}
buf += SZ_SG_HEADER;
__get_user(opcode, buf);
+ mutex_lock(&sfp->f_mutex);
if (sfp->next_cmd_len > 0) {
if (sfp->next_cmd_len > MAX_COMMAND_SIZE) {
SCSI_LOG_TIMEOUT(1, printk("sg_write: command length too long\n"));
@@ -614,6 +616,7 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
if ((opcode >= 0xc0) && old_hdr.twelve_byte)
cmd_size = 12;
}
+ mutex_unlock(&sfp->f_mutex);
SCSI_LOG_TIMEOUT(4, printk(
"sg_write: scsi opcode=0x%02x, cmd_size=%d\n", (int) opcode, cmd_size));
/* Determine buffer size. */
@@ -712,7 +715,7 @@ sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,
sg_remove_request(sfp, srp);
return -EINVAL; /* either MMAP_IO or DIRECT_IO (not both) */
}
- if (sg_res_in_use(sfp)) {
+ if (sfp->res_in_use) {
sg_remove_request(sfp, srp);
return -EBUSY; /* reserve buffer already being used */
}
@@ -878,18 +881,22 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
result = get_user(val, ip);
if (result)
return result;
+ mutex_lock(&sfp->f_mutex);
if (val) {
sfp->low_dma = 1;
- if ((0 == sfp->low_dma) && (0 == sg_res_in_use(sfp))) {
+ if ((0 == sfp->low_dma) && (0 == sfp->res_in_use)) {
val = (int) sfp->reserve.bufflen;
sg_remove_scat(&sfp->reserve);
sg_build_reserve(sfp, val);
}
} else {
- if (sdp->detached)
+ if (sdp->detached) {
+ mutex_unlock(&sfp->f_mutex);
return -ENODEV;
+ }
sfp->low_dma = sdp->device->host->unchecked_isa_dma;
}
+ mutex_unlock(&sfp->f_mutex);
return 0;
case SG_GET_LOW_DMA:
return put_user((int) sfp->low_dma, ip);
@@ -955,12 +962,18 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
return -EINVAL;
val = min_t(int, val,
queue_max_sectors(sdp->device->request_queue) * 512);
+ mutex_lock(&sfp->f_mutex);
if (val != sfp->reserve.bufflen) {
- if (sg_res_in_use(sfp) || sfp->mmap_called)
+ if (sfp->mmap_called ||
+ sfp->res_in_use) {
+ mutex_unlock(&sfp->f_mutex);
return -EBUSY;
+ }
+
sg_remove_scat(&sfp->reserve);
sg_build_reserve(sfp, val);
}
+ mutex_unlock(&sfp->f_mutex);
return 0;
case SG_GET_RESERVED_SIZE:
val = min_t(int, sfp->reserve.bufflen,
@@ -1685,13 +1698,22 @@ static int sg_start_req(Sg_request *srp, unsigned char *cmd)
md = &map_data;
if (md) {
- if (!sg_res_in_use(sfp) && dxfer_len <= rsv_schp->bufflen)
+ mutex_lock(&sfp->f_mutex);
+ if (dxfer_len <= rsv_schp->bufflen &&
+ !sfp->res_in_use) {
+ sfp->res_in_use = 1;
sg_link_reserve(sfp, srp, dxfer_len);
- else {
+ } else if ((hp->flags & SG_FLAG_MMAP_IO) && sfp->res_in_use) {
+ mutex_unlock(&sfp->f_mutex);
+ return -EBUSY;
+ } else {
res = sg_build_indirect(req_schp, sfp, dxfer_len);
- if (res)
+ if (res) {
+ mutex_unlock(&sfp->f_mutex);
return res;
+ }
}
+ mutex_unlock(&sfp->f_mutex);
md->pages = req_schp->pages;
md->page_order = req_schp->page_order;
@@ -2083,6 +2105,7 @@ sg_add_sfp(Sg_device * sdp, int dev)
rwlock_init(&sfp->rq_list_lock);
kref_init(&sfp->f_ref);
+ mutex_init(&sfp->f_mutex);
sfp->timeout = SG_DEFAULT_TIMEOUT;
sfp->timeout_user = SG_DEFAULT_TIMEOUT_USER;
sfp->force_packid = SG_DEF_FORCE_PACK_ID;
@@ -2152,20 +2175,6 @@ static void sg_remove_sfp(struct kref *kref)
schedule_work(&sfp->ew.work);
}
-static int
-sg_res_in_use(Sg_fd * sfp)
-{
- const Sg_request *srp;
- unsigned long iflags;
-
- read_lock_irqsave(&sfp->rq_list_lock, iflags);
- for (srp = sfp->headrp; srp; srp = srp->nextrp)
- if (srp->res_used)
- break;
- read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
- return srp ? 1 : 0;
-}
-
#ifdef CONFIG_SCSI_PROC_FS
static int
sg_idr_max_id(int id, void *p, void *data)
--
2.7.4
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