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Fix compat regression in process_vm_rw()

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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: c3973b401e ("mm: remove compat_process_vm_{readv,writev}")
Reported-and-tested-by: Kyle Huey <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Acked-by: Al Viro <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jens Axboe authored and Linus Torvalds committed 2020-10-27 09:57:46 -07:00
1 parent 4525c8781e
commit 38dc5079da
1 file changed
+2 -1
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mm/process_vm_access.c
+2 -1
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@@ -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;