Commit 38dc5079 authored Oct 26, 2020 by Jens Axboe Committed by Linus Torvalds Oct 27, 2020

Fix compat regression in process_vm_rw()



The removal of compat_process_vm_{readv,writev} didn't change
process_vm_rw(), which always assumes it's not doing a compat syscall.

Instead of passing in 'false' unconditionally for 'compat', make it
conditional on in_compat_syscall().

[ Both Al and Christoph point out that trying to access a 64-bit process
  from a 32-bit one cannot work anyway, and is likely better prohibited,
  but that's a separate issue    - Linus ]

Fixes: c3973b40 ("mm: remove compat_process_vm_{readv,writev}")
Reported-and-tested-by: Kyle Huey <me@kylehuey.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4525c878

mm/process_vm_access.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -273,7 +273,8 @@ static ssize_t process_vm_rw(pid_t pid,
		return rc;
		if (!iov_iter_count(&iter))
		goto free_iov_l;
		iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false);
		iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r,
		in_compat_syscall());
		if (IS_ERR(iov_r)) {
		rc = PTR_ERR(iov_r);
		goto free_iov_l;

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