Commit febfbf76 authored by Colin Ian King's avatar Colin Ian King Committed by Jens Axboe
Browse files

io_uring/kbuf: fix unintentional sign extension on shift of reg.bgid 



Shifting reg.bgid << IORING_OFF_PBUF_SHIFT results in a promotion
from __u16 to a 32 bit signed integer, this is then sign extended
to a 64 bit unsigned long on 64 bit architectures. If reg.bgid is
greater than 0x7fff then this leads to a sign extended result where
all the upper 32 bits of mmap_offset are set to 1. Fix this by
casting reg.bgid to the same type as mmap_offset before performing
the shift.

Fixes: ef62de3c ("io_uring/kbuf: use region api for pbuf rings")
Signed-off-by: default avatarColin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20241204153923.401674-1-colin.i.king@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 546d1914

io_uring/kbuf.c

+1 −1
Original line number Diff line number Diff line
@@ -640,7 +640,7 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg) 
			return -ENOMEM;

	}



	mmap_offset = reg.bgid << IORING_OFF_PBUF_SHIFT;

	mmap_offset = (unsigned long)reg.bgid << IORING_OFF_PBUF_SHIFT;

	ring_size = flex_array_size(br, bufs, reg.ring_entries);



	memset(&rd, 0, sizeof(rd));