iov_iter: saner checks for attempt to copy to/from iterator

instead of "don't do it to ITER_PIPE" check for ->data_source being
false on copying from iterator.  Check for !->data_source for
copying to iterator, while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 020e009..98e8425 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -520,6 +520,8 @@ static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
 
 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
+       if (WARN_ON_ONCE(i->data_source))
+               return 0;
        if (unlikely(iov_iter_is_pipe(i)))
                return copy_pipe_to_iter(addr, bytes, i);
        if (user_backed_iter(i))
@@ -606,6 +608,8 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
  */
 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
+       if (WARN_ON_ONCE(i->data_source))
+               return 0;
        if (unlikely(iov_iter_is_pipe(i)))
                return copy_mc_pipe_to_iter(addr, bytes, i);
        if (user_backed_iter(i))
@@ -622,10 +626,9 @@ EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
 
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 {
-       if (unlikely(iov_iter_is_pipe(i))) {
-               WARN_ON(1);
+       if (WARN_ON_ONCE(!i->data_source))
                return 0;
-       }
+
        if (user_backed_iter(i))
                might_fault();
        iterate_and_advance(i, bytes, base, len, off,
@@ -639,10 +642,9 @@ EXPORT_SYMBOL(_copy_from_iter);
 
 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 {
-       if (unlikely(iov_iter_is_pipe(i))) {
-               WARN_ON(1);
+       if (WARN_ON_ONCE(!i->data_source))
                return 0;
-       }
+
        iterate_and_advance(i, bytes, base, len, off,
                __copy_from_user_inatomic_nocache(addr + off, base, len),
                memcpy(addr + off, base, len)
@@ -671,10 +673,9 @@ EXPORT_SYMBOL(_copy_from_iter_nocache);
  */
 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 {
-       if (unlikely(iov_iter_is_pipe(i))) {
-               WARN_ON(1);
+       if (WARN_ON_ONCE(!i->data_source))
                return 0;
-       }
+
        iterate_and_advance(i, bytes, base, len, off,
                __copy_from_user_flushcache(addr + off, base, len),
                memcpy_flushcache(addr + off, base, len)
@@ -714,6 +715,8 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
        size_t res = 0;
        if (!page_copy_sane(page, offset, bytes))
                return 0;
+       if (WARN_ON_ONCE(i->data_source))
+               return 0;
        if (unlikely(iov_iter_is_pipe(i)))
                return copy_page_to_iter_pipe(page, offset, bytes, i);
        page += offset / PAGE_SIZE; // first subpage
@@ -811,9 +814,8 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt
                kunmap_atomic(kaddr);
                return 0;
        }
-       if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
+       if (WARN_ON_ONCE(!i->data_source)) {
                kunmap_atomic(kaddr);
-               WARN_ON(1);
                return 0;
        }
        iterate_and_advance(i, bytes, base, len, off,
@@ -1525,10 +1527,9 @@ size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 {
        __wsum sum, next;
        sum = *csum;
-       if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
-               WARN_ON(1);
+       if (WARN_ON_ONCE(!i->data_source))
                return 0;
-       }
+
        iterate_and_advance(i, bytes, base, len, off, ({
                next = csum_and_copy_from_user(base, addr + off, len);
                sum = csum_block_add(sum, next, off);
@@ -1548,6 +1549,8 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
        struct csum_state *csstate = _csstate;
        __wsum sum, next;
 
+       if (WARN_ON_ONCE(i->data_source))
+               return 0;
        if (unlikely(iov_iter_is_discard(i))) {
                // can't use csum_memcpy() for that one - data is not copied
                csstate->csum = csum_block_add(csstate->csum,