lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe() (ca146f6f) · Commits · 戴 / test

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:

Ross Zwisler <ross.zwisler@linux.intel.com> Tested-by:

Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by:

Dan Williams <dan.j.williams@intel.com> Acked-by:

Al 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: ("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:

Ingo Molnar <mingo@kernel.org>

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,

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