Commit 33844e66 authored by Al Viro's avatar Al Viro
Browse files

[iov_iter] fix iterate_all_kinds() on empty iterators 



Problem similar to ones dealt with in "fold checks into iterate_and_advance()"
and followups, except that in this case we really want to do nothing when
asked for zero-length operation - unlike zero-length iterate_and_advance(),
zero-length iterate_all_kinds() has no side effects, and callers are simpler
that way.

That got exposed when copy_from_iter_full() had been used by tipc, which
builds an msghdr with zero payload and (now) feeds it to a primitive
based on iterate_all_kinds() instead of iterate_and_advance().

Reported-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Tested-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent c00d2c7e

lib/iov_iter.c

+26 −29
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ 
}



#define iterate_all_kinds(i, n, v, I, B, K) {			\

	if (likely(n)) {					\

		size_t skip = i->iov_offset;			\

		if (unlikely(i->type & ITER_BVEC)) {		\

			struct bio_vec v;			\
@@ -87,6 +88,7 @@ 
			struct iovec v;				\

			iterate_iovec(i, n, v, iov, skip, (I))	\

		}						\

	}							\

}



#define iterate_and_advance(i, n, v, I, B, K) {			\
@@ -576,7 +578,7 @@ bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i) 
		WARN_ON(1);

		return false;

	}

	if (unlikely(i->count < bytes))				\

	if (unlikely(i->count < bytes))

		return false;



	iterate_all_kinds(i, bytes, v, ({
@@ -620,7 +622,7 @@ bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i) 
		WARN_ON(1);

		return false;

	}

	if (unlikely(i->count < bytes))				\

	if (unlikely(i->count < bytes))

		return false;

	iterate_all_kinds(i, bytes, v, ({

		if (__copy_from_user_nocache((to += v.iov_len) - v.iov_len,
@@ -837,11 +839,8 @@ unsigned long iov_iter_alignment(const struct iov_iter *i) 
	unsigned long res = 0;

	size_t size = i->count;



	if (!size)

		return 0;



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

		if (i->iov_offset && allocated(&i->pipe->bufs[i->idx]))

		if (size && i->iov_offset && allocated(&i->pipe->bufs[i->idx]))

			return size | i->iov_offset;

		return size;

	}
@@ -858,8 +857,6 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i) 
{

	unsigned long res = 0;

	size_t size = i->count;

	if (!size)

		return 0;



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

		WARN_ON(1);
@@ -908,6 +905,9 @@ static ssize_t pipe_get_pages(struct iov_iter *i, 
	size_t capacity;

	int idx;



	if (!maxsize)

		return 0;



	if (!sanity(i))

		return -EFAULT;
@@ -926,9 +926,6 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, 
	if (maxsize > i->count)

		maxsize = i->count;



	if (!maxsize)

		return 0;



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

		return pipe_get_pages(i, pages, maxsize, maxpages, start);

	iterate_all_kinds(i, maxsize, v, ({
@@ -975,6 +972,9 @@ static ssize_t pipe_get_pages_alloc(struct iov_iter *i, 
	int idx;

	int npages;



	if (!maxsize)

		return 0;



	if (!sanity(i))

		return -EFAULT;
@@ -1006,9 +1006,6 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, 
	if (maxsize > i->count)

		maxsize = i->count;



	if (!maxsize)

		return 0;



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

		return pipe_get_pages_alloc(i, pages, maxsize, start);

	iterate_all_kinds(i, maxsize, v, ({

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