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lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()

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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: 8780356ef6 ("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>
This commit is contained in:
Dan Williams 2018-07-08 13:46:12 -07:00 committed by Ingo Molnar
parent abd08d7d24
commit ca146f6f09
1 changed files with 33 additions and 4 deletions
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37
lib/iov_iter.c
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@ -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,