loop: use sysfs_emit() in the sysfs xxx show()

sprintf does not know the PAGE_SIZE maximum of the temporary buffer
used for outputting sysfs content and it's possible to overrun the
PAGE_SIZE buffer length.

Use a generic sysfs_emit function that knows the size of the
temporary buffer and ensures that no overrun is done for offset
attribute in
loop_attr_[offset|sizelimit|autoclear|partscan|dio]_show() callbacks.

Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Link: https://lore.kernel.org/r/20220215213310.7264-2-kch@nvidia.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index bdea448..a55e5ed 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -680,33 +680,33 @@ static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
 
 static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
 {
-       return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
+       return sysfs_emit(buf, "%llu\n", (unsigned long long)lo->lo_offset);
 }
 
 static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
 {
-       return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
+       return sysfs_emit(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
 }
 
 static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
 {
        int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
 
-       return sprintf(buf, "%s\n", autoclear ? "1" : "0");
+       return sysfs_emit(buf, "%s\n", autoclear ? "1" : "0");
 }
 
 static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
 {
        int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
 
-       return sprintf(buf, "%s\n", partscan ? "1" : "0");
+       return sysfs_emit(buf, "%s\n", partscan ? "1" : "0");
 }
 
 static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf)
 {
        int dio = (lo->lo_flags & LO_FLAGS_DIRECT_IO);
 
-       return sprintf(buf, "%s\n", dio ? "1" : "0");
+       return sysfs_emit(buf, "%s\n", dio ? "1" : "0");
 }
 
 LOOP_ATTR_RO(backing_file);