md: Replace snprintf with scnprintf

Current code produces a warning as shown below when total characters
in the constituent block device names plus the slashes exceeds 200.
snprintf() returns the number of characters generated from the given
input, which could cause the expression “200 – len” to wrap around
to a large positive number. Fix this by using scnprintf() instead,
which returns the actual number of characters written into the buffer.

[ 1513.267938] ------------[ cut here ]------------
[ 1513.267943] WARNING: CPU: 15 PID: 37247 at <snip>/lib/vsprintf.c:2509 vsnprintf+0x2c8/0x510
[ 1513.267944] Modules linked in:  <snip>
[ 1513.267969] CPU: 15 PID: 37247 Comm: mdadm Not tainted 5.4.0-1085-azure #90~18.04.1-Ubuntu
[ 1513.267969] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 05/09/2022
[ 1513.267971] RIP: 0010:vsnprintf+0x2c8/0x510
<-snip->
[ 1513.267982] Call Trace:
[ 1513.267986]  snprintf+0x45/0x70
[ 1513.267990]  ? disk_name+0x71/0xa0
[ 1513.267993]  dump_zones+0x114/0x240 [raid0]
[ 1513.267996]  ? _cond_resched+0x19/0x40
[ 1513.267998]  raid0_run+0x19e/0x270 [raid0]
[ 1513.268000]  md_run+0x5e0/0xc50
[ 1513.268003]  ? security_capable+0x3f/0x60
[ 1513.268005]  do_md_run+0x19/0x110
[ 1513.268006]  md_ioctl+0x195e/0x1f90
[ 1513.268007]  blkdev_ioctl+0x91f/0x9f0
[ 1513.268010]  block_ioctl+0x3d/0x50
[ 1513.268012]  do_vfs_ioctl+0xa9/0x640
[ 1513.268014]  ? __fput+0x162/0x260
[ 1513.268016]  ksys_ioctl+0x75/0x80
[ 1513.268017]  __x64_sys_ioctl+0x1a/0x20
[ 1513.268019]  do_syscall_64+0x5e/0x200
[ 1513.268021]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 766038846e875 ("md/raid0: replace printk() with pr_*()")
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Song Liu <song@kernel.org>

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 78addfe4a0c925c51c58b4f6d20cfa4080e1924a..857c49399c28ed48db0a9edee3dc732f53e69f11 100644 (file)
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -47,7 +47,7 @@ static void dump_zones(struct mddev *mddev)
                int len = 0;
 
                for (k = 0; k < conf->strip_zone[j].nb_dev; k++)
-                       len += snprintf(line+len, 200-len, "%s%pg", k?"/":"",
+                       len += scnprintf(line+len, 200-len, "%s%pg", k?"/":"",
                                conf->devlist[j * raid_disks + k]->bdev);
                pr_debug("md: zone%d=[%s]\n", j, line);