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    Subject[PATCH 5.17 0851/1126] loop: use sysfs_emit() in the sysfs xxx show()
    Date
    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 19fe19eaa50e..e65d1e24cab3 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


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