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

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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: ef62de3c4a ("io_uring/kbuf: use region api for pbuf rings")
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20241204153923.401674-1-colin.i.king@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Colin Ian King 2024-12-04 15:39:23 +00:00 committed by Jens Axboe
parent 546d191427
commit febfbf7671
1 changed files with 1 additions and 1 deletions
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2
io_uring/kbuf.c
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@ -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));