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vfs: ioctl: prevent double-fetch in dedupe ioctl
This prevents a double-fetch from user space that can lead to to an
undersized allocation and heap overflow.

Fixes: 54dbc15 ("vfs: hoist the btrfs deduplication ioctl to the vfs")
Signed-off-by: Scott Bauer <sbauer@plzdonthack.me>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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ScottyBauer authored and torvalds committed Jul 28, 2016
1 parent 884316d commit 10eec60
Showing 1 changed file with 1 addition and 0 deletions.
1 change: 1 addition & 0 deletions fs/ioctl.c
Expand Up @@ -590,6 +590,7 @@ static long ioctl_file_dedupe_range(struct file *file, void __user *arg)
goto out;
}

same->dest_count = count;
ret = vfs_dedupe_file_range(file, same);
if (ret)
goto out;
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