[PATCH 5.16 0768/1017] loop: use sysfs_emit() in the sysfs xxx show()

Greg Kroah-Hartman
2022-04-05T13:24:04Z

From: Chaitanya Kulkarni <kch@nvidia.com>

[ Upstream commit b27824d31f09ea7b4a6ba2c1b18bd328df3e8bed ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/loop.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index fdb4798cb006..1422967bf5c1 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -681,33 +681,33 @@ 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);
--
2.34.1