linux-kernel - [PATCH v2] block/compat_ioctl: fix range check in BLKGETSIZE

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Date:   Thu, 14 Apr 2022 15:40:56 -0700
From:   Khazhismel Kumykov <khazhy@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Khazhismel Kumykov <khazhy@...gle.com>,
        Bart Van Assche <bvanassche@....org>
Subject: [PATCH v2] block/compat_ioctl: fix range check in BLKGETSIZE

kernel ulong and compat_ulong_t may not be same width. Use type directly
to eliminate mismatches.

This would result in truncation rather than EFBIG for 32bit mode for
large disks.

Reviewed-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Khazhismel Kumykov <khazhy@...gle.com>
---
 block/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

v2: addressed bart's comment

diff --git a/block/ioctl.c b/block/ioctl.c
index 4a86340133e4..f8703db99c73 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -629,7 +629,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 		return compat_put_long(argp,
 			(bdev->bd_disk->bdi->ra_pages * PAGE_SIZE) / 512);
 	case BLKGETSIZE:
-		if (bdev_nr_sectors(bdev) > ~0UL)
+		if (bdev_nr_sectors(bdev) > ~(compat_ulong_t)0)
 			return -EFBIG;
 		return compat_put_ulong(argp, bdev_nr_sectors(bdev));
 
-- 
2.36.0.rc0.470.gd361397f0d-goog