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authorMing Lei <ming.lei@canonical.com>2015-08-09 03:41:50 -0400
committerJens Axboe <axboe@fb.com>2015-08-15 09:45:19 -0600
commit596f5aad2a704b72934e5abec1b1b4114c16f45b (patch)
tree023d281a8921d55c79050e35117d4a67df53a485 /block/blk-mq-sysfs.c
parent2ec3182f9c20a9eef0dacc0512cf2ca2df7be5ad (diff)
downloadlinux-linaro-stable-596f5aad2a704b72934e5abec1b1b4114c16f45b.tar.gz
blk-mq: fix buffer overflow when reading sysfs file of 'pending'
There may be lots of pending requests so that the buffer of PAGE_SIZE can't hold them at all. One typical example is scsi-mq, the queue depth(.can_queue) of scsi_host and blk-mq is quite big but scsi_device's queue_depth is a bit small(.cmd_per_lun), then it is quite easy to have lots of pending requests in hw queue. This patch fixes the following warning and the related memory destruction. [ 359.025101] fill_read_buffer: blk_mq_hw_sysfs_show+0x0/0x7d returned bad count^M [ 359.055595] irq event stamp: 15537^M [ 359.055606] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC ^M [ 359.055614] Dumping ftrace buffer:^M [ 359.055660] (ftrace buffer empty)^M [ 359.055672] Modules linked in: nbd ipv6 kvm_intel kvm serio_raw^M [ 359.055678] CPU: 4 PID: 21631 Comm: stress-ng-sysfs Not tainted 4.2.0-rc5-next-20150805 #434^M [ 359.055679] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011^M [ 359.055682] task: ffff8802161cc000 ti: ffff88021b4a8000 task.ti: ffff88021b4a8000^M [ 359.055693] RIP: 0010:[<ffffffff811541c5>] [<ffffffff811541c5>] __kmalloc+0xe8/0x152^M Cc: <stable@vger.kernel.org> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq-sysfs.c')
-rw-r--r--block/blk-mq-sysfs.c25
1 files changed, 18 insertions, 7 deletions
diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index b79685e06b70..279c5d674edf 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -141,15 +141,26 @@ static ssize_t blk_mq_sysfs_completed_show(struct blk_mq_ctx *ctx, char *page)
static ssize_t sysfs_list_show(char *page, struct list_head *list, char *msg)
{
- char *start_page = page;
struct request *rq;
+ int len = snprintf(page, PAGE_SIZE - 1, "%s:\n", msg);
+
+ list_for_each_entry(rq, list, queuelist) {
+ const int rq_len = 2 * sizeof(rq) + 2;
+
+ /* if the output will be truncated */
+ if (PAGE_SIZE - 1 < len + rq_len) {
+ /* backspacing if it can't hold '\t...\n' */
+ if (PAGE_SIZE - 1 < len + 5)
+ len -= rq_len;
+ len += snprintf(page + len, PAGE_SIZE - 1 - len,
+ "\t...\n");
+ break;
+ }
+ len += snprintf(page + len, PAGE_SIZE - 1 - len,
+ "\t%p\n", rq);
+ }
- page += sprintf(page, "%s:\n", msg);
-
- list_for_each_entry(rq, list, queuelist)
- page += sprintf(page, "\t%p\n", rq);
-
- return page - start_page;
+ return len;
}
static ssize_t blk_mq_sysfs_rq_list_show(struct blk_mq_ctx *ctx, char *page)