Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ca146f6f authored by Dan Williams's avatar Dan Williams Committed by Ingo Molnar
Browse files

lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe() 



By mistake the ITER_PIPE early-exit / warning from copy_from_iter() was
cargo-culted in _copy_to_iter_mcsafe() rather than a machine-check-safe
version of copy_to_iter_pipe().

Implement copy_pipe_to_iter_mcsafe() being careful to return the
indication of short copies due to a CPU exception.

Without this regression-fix all splice reads to dax-mode files fail.

Reported-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Tested-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Acked-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Fixes: 8780356e ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
Link: http://lkml.kernel.org/r/153108277278.37979.3327916996902264102.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent abd08d7d

lib/iov_iter.c

+33 −4
Original line number Diff line number Diff line
@@ -596,6 +596,37 @@ static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset, 
	return ret;

}



static size_t copy_pipe_to_iter_mcsafe(const void *addr, size_t bytes,

				struct iov_iter *i)

{

	struct pipe_inode_info *pipe = i->pipe;

	size_t n, off, xfer = 0;

	int idx;



	if (!sanity(i))

		return 0;



	bytes = n = push_pipe(i, bytes, &idx, &off);

	if (unlikely(!n))

		return 0;

	for ( ; n; idx = next_idx(idx, pipe), off = 0) {

		size_t chunk = min_t(size_t, n, PAGE_SIZE - off);

		unsigned long rem;



		rem = memcpy_mcsafe_to_page(pipe->bufs[idx].page, off, addr,

				chunk);

		i->idx = idx;

		i->iov_offset = off + chunk - rem;

		xfer += chunk - rem;

		if (rem)

			break;

		n -= chunk;

		addr += chunk;

	}

	i->count -= xfer;

	return xfer;

}



/**

 * _copy_to_iter_mcsafe - copy to user with source-read error exception handling

 * @addr: source kernel address
@@ -627,10 +658,8 @@ size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i) 
	const char *from = addr;

	unsigned long rem, curr_addr, s_addr = (unsigned long) addr;



	if (unlikely(i->type & ITER_PIPE)) {

		WARN_ON(1);

		return 0;

	}

	if (unlikely(i->type & ITER_PIPE))

		return copy_pipe_to_iter_mcsafe(addr, bytes, i);

	if (iter_is_iovec(i))

		might_fault();

	iterate_and_advance(i, bytes, v,