[PATCH] uml: hostfs - fix possible PAGE_CACHE_SHIFT overflows (30f04a4e) · Commits · 戴 / test

Prevent page->index << PAGE_CACHE_SHIFT from overflowing. There is a casting there, but was added without care, so it's at the wrong place. Note the extra parens around the shift - "+" is higher precedence than "<<", leading to a GCC warning which saved all us. Signed-off-by:

Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

fs/hostfs/hostfs_kern.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -501,11 +501,16 @@ int hostfs_commit_write(struct file file, struct page page, unsigned from,
		long long start;
		int err = 0;

		start = (long long) (page->index << PAGE_CACHE_SHIFT) + from;
		start = (((long long) page->index) << PAGE_CACHE_SHIFT) + from;
		buffer = kmap(page);
		err = write_file(FILE_HOSTFS_I(file)->fd, &start, buffer + from,
		to - from);
		if(err > 0) err = 0;

		/* Actually, if !err, write_file has added to-from to start, so, despite
		* the appearance, we are comparing i_size against the _last_ written
		* location, as we should. */

		if(!err && (start > inode->i_size))
		inode->i_size = start;

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