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Subject[34-longterm 066/209] bio: take care not overflow page count when mapping/copying user data
Date
From: Jens Axboe <jaxboe@fusionio.com>

=====================================================================
| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|
=====================================================================

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: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/bio.c | 14 +++++++++++++-
1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/fs/bio.c b/fs/bio.c
index 75ea4c3..b3e0174 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -834,6 +834,12 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
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(struct request_queue *q,
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(struct request_queue *q,
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) {
--
1.7.4.4


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