From: Kees Cook Date: Fri, 11 Aug 2023 05:45:32 +0000 (-0700) Subject: printk: ringbuffer: Fix truncating buffer size min_t cast X-Git-Tag: v6.6.17~4001^2~4 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=53e9e33ede37a247d926db5e4a9e56b55204e66c;p=platform%2Fkernel%2Flinux-rpi.git printk: ringbuffer: Fix truncating buffer size min_t cast 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 Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: John Ogness Reported-by: Vijay Balakrishna Link: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@linux.microsoft.com/ Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Tested-by: Vijay Balakrishna Tested-by: Guilherme G. Piccoli # Steam Deck Reviewed-by: Tyler Hicks (Microsoft) Tested-by: Tyler Hicks (Microsoft) Reviewed-by: John Ogness Reviewed-by: Sergey Senozhatsky Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230811054528.never.165-kees@kernel.org --- 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;