If an output buffer size exceeded U16_MAX, the min_t(u16, ...) cast in copy_data() was causing writes to truncate. This manifested as output bytes being skipped, seen as %NUL bytes in pstore dumps when the available record size was larger than 65536. Fix the cast to no longer truncate the calculation. Cc: Petr Mladek <pmladek@xxxxxxxx> Cc: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: John Ogness <john.ogness@xxxxxxxxxxxxx> Reported-by: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx> Closes: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@xxxxxxxxxxxxxxxxxxx/ Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- kernel/printk/printk_ringbuffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 2dc4d5a1f1ff..fde338606ce8 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -1735,7 +1735,7 @@ static bool copy_data(struct prb_data_ring *data_ring, if (!buf || !buf_size) return true; - data_size = min_t(u16, buf_size, len); + data_size = min_t(unsigned int, buf_size, len); memcpy(&buf[0], data, data_size); /* LMM(copy_data:A) */ return true; -- 2.34.1
