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    Subject[PATCH 5.15 814/917] zram: off by one in read_block_state()
    Date
    From: Dan Carpenter <dan.carpenter@oracle.com>

    [ Upstream commit a88e03cf3d190cf46bc4063a9b7efe87590de5f4 ]

    snprintf() returns the number of bytes it would have printed if there
    were space. But it does not count the NUL terminator. So that means
    that if "count == copied" then this has already overflowed by one
    character.

    This bug likely isn't super harmful in real life.

    Link: https://lkml.kernel.org/r/20210916130404.GA25094@kili
    Fixes: c0265342bff4 ("zram: introduce zram memory tracking")
    Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/block/zram/zram_drv.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
    index fcaf2750f68f7..6383c81ac5b37 100644
    --- a/drivers/block/zram/zram_drv.c
    +++ b/drivers/block/zram/zram_drv.c
    @@ -910,7 +910,7 @@ static ssize_t read_block_state(struct file *file, char __user *buf,
    zram_test_flag(zram, index, ZRAM_HUGE) ? 'h' : '.',
    zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.');

    - if (count < copied) {
    + if (count <= copied) {
    zram_slot_unlock(zram, index);
    break;
    }
    --
    2.33.0


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