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Subject[PATCH] [128/223] bio: take care not overflow page count when mapping/copying user data
Date
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Jens Axboe <jaxboe@fusionio.com>

commit cb4644cac4a2797afc847e6c92736664d4b0ea34 upstream.

If the iovec is being set up in a way that causes uaddr + PAGE_SIZE
to overflow, we could end up attempting to map a huge number of
pages. Check for this invalid input type.

Reported-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
fs/bio.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

Index: linux/fs/bio.c
===================================================================
--- linux.orig/fs/bio.c
+++ linux/fs/bio.c
@@ -834,6 +834,12 @@ struct bio *bio_copy_user_iov(struct req
end = (uaddr + iov[i].iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
start = uaddr >> PAGE_SHIFT;

+ /*
+ * Overflow, abort
+ */
+ if (end < start)
+ return ERR_PTR(-EINVAL);
+
nr_pages += end - start;
len += iov[i].iov_len;
}
@@ -961,6 +967,12 @@ static struct bio *__bio_map_user_iov(st
unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;

+ /*
+ * Overflow, abort
+ */
+ if (end < start)
+ return ERR_PTR(-EINVAL);
+
nr_pages += end - start;
/*
* buffer must be aligned to at least hardsector size for now
@@ -988,7 +1000,7 @@ static struct bio *__bio_map_user_iov(st
unsigned long start = uaddr >> PAGE_SHIFT;
const int local_nr_pages = end - start;
const int page_limit = cur_page + local_nr_pages;
-
+
ret = get_user_pages_fast(uaddr, local_nr_pages,
write_to_vm, &pages[cur_page]);
if (ret < local_nr_pages) {

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