From 38dc5079da7081e8b09b14e255e9da82c451a531 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 26 Oct 2020 18:03:18 -0600
Subject: [PATCH] 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: c3973b401ef2 ("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>
---
mm/process_vm_access.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index fd12da80b6f27..05676722d9cd6 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -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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