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

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Message-Id: <20180406222350.174104-1-khazhy@google.com>
Date:   Fri,  6 Apr 2018 15:23:50 -0700
From:   Khazhismel Kumykov <khazhy@...gle.com>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Khazhismel Kumykov <khazhy@...gle.com>
Subject: [PATCH] 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.

Signed-off-by: Khazhismel Kumykov <khazhy@...gle.com>
---
 block/compat_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index 6ca015f92766..3a2c77f07da8 100644
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -388,7 +388,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 		return 0;
 	case BLKGETSIZE:
 		size = i_size_read(bdev->bd_inode);
-		if ((size >> 9) > ~0UL)
+		if ((size >> 9) > ~((compat_ulong_t)0UL))
 			return -EFBIG;
 		return compat_put_ulong(arg, size >> 9);
 
-- 
2.17.0.484.g0c8726318c-goog


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