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Commit f7009264 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

iov_iter_advance() fix 



iov_iter_advance() skips over zero-length iovecs, however it does not properly
terminate at the end of the iovec array.  Fix this by checking against
i->count before we skip a zero-length iov.

The bug was reproduced with a test program that continually randomly creates
iovs to writev.  The fix was also verified with the same program and also it
could verify that the correct data was contained in the file after each
writev.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Tested-by: default avatar"Kevin Coffman" <kwc@citi.umich.edu>
Cc: "Alexey Dobriyan" <adobriyan@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21bbb39c

mm/filemap.c

+10 −12
Original line number Diff line number Diff line
@@ -1742,21 +1742,27 @@ size_t iov_iter_copy_from_user(struct page *page, 
}

EXPORT_SYMBOL(iov_iter_copy_from_user);



static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes)

void iov_iter_advance(struct iov_iter *i, size_t bytes)

{

	BUG_ON(i->count < bytes);



	if (likely(i->nr_segs == 1)) {

		i->iov_offset += bytes;

		i->count -= bytes;

	} else {

		const struct iovec *iov = i->iov;

		size_t base = i->iov_offset;



		/*

		 * The !iov->iov_len check ensures we skip over unlikely

		 * zero-length segments.

		 * zero-length segments (without overruning the iovec).

		 */

		while (bytes || !iov->iov_len) {

			int copy = min(bytes, iov->iov_len - base);

		while (bytes || unlikely(!iov->iov_len && i->count)) {

			int copy;



			copy = min(bytes, iov->iov_len - base);

			BUG_ON(!i->count || i->count < copy);

			i->count -= copy;

			bytes -= copy;

			base += copy;

			if (iov->iov_len == base) {
@@ -1768,14 +1774,6 @@ static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes) 
		i->iov_offset = base;

	}

}



void iov_iter_advance(struct iov_iter *i, size_t bytes)

{

	BUG_ON(i->count < bytes);



	__iov_iter_advance_iov(i, bytes);

	i->count -= bytes;

}

EXPORT_SYMBOL(iov_iter_advance);



/*