From: Colin Ian King Date: Wed, 4 Dec 2024 15:39:23 +0000 (+0000) Subject: io_uring/kbuf: fix unintentional sign extension on shift of reg.bgid X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=febfbf767174b8a027efb7aa434f9a9416adc23d;p=users%2Fjedix%2Flinux-maple.git 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: ef62de3c4ad5 ("io_uring/kbuf: use region api for pbuf rings") Signed-off-by: Colin Ian King Link: https://lore.kernel.org/r/20241204153923.401674-1-colin.i.king@gmail.com Signed-off-by: Jens Axboe --- diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index e91260a6156ba..15e5e6ec59680 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -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));