From: Kees Cook > Sent: 11 August 2023 06:46 > > 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. > ... > 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); I'd noticed that during one of my test compiles while looking at making min() less fussy. A better fix would be: data_size = min(buf_size + 0u, len); Or put an ack on my patch 3/5 to minmax.h and then min(buf_size, len) will be fine (because both arguments are unsigned). David > > memcpy(&buf[0], data, data_size); /* LMM(copy_data:A) */ > return true; > -- > 2.34.1 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
