highmem: fix a memory copy problem in memcpy_from_folio

commit 73424d00dc63ba681856e06cfb0a5abbdb62e2b5 upstream.

Clang static checker complains that value stored to 'from' is never read.
And memcpy_from_folio() only copy the last chunk memory from folio to
destination.  Use 'to += chunk' to replace 'from += chunk' to fix this
typo problem.

Link: https://lkml.kernel.org/r/20231130034017.1210429-1-suhui@nfschina.com
Fixes: b23d03ef7af5 ("highmem: add memcpy_to_folio() and memcpy_from_folio()")
Signed-off-by: Su Hui <suhui@nfschina.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Tom Rix <trix@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 99c474d..75607d4 100644 (file)
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -454,7 +454,7 @@ static inline void memcpy_from_folio(char *to, struct folio *folio,
                memcpy(to, from, chunk);
                kunmap_local(from);
 
-               from += chunk;
+               to += chunk;
                offset += chunk;
                len -= chunk;
        } while (len > 0);