[PATCH] btrfs: fix extent map use-after-free when adding pages to compressed bio

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



At add_ra_bio_pages() we are accessing the extent map to calculate
'add_size' after we dropped our reference on the extent map, resulting
in a use-after-free. Fix this by computing 'add_size' before dropping our
extent map reference.

Reported-by: syzbot+853d80cba98ce1157ae6@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/linux-btrfs/000000000000038144061c6d18f2@xxxxxxxxxx/
Fixes: 6a4049102055 ("btrfs: subpage: make add_ra_bio_pages() compatible")
CC: stable@xxxxxxxxxxxxxxx # 6.1+
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index a149f3659b15..a8e2c461aff7 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -515,6 +515,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			put_page(page);
 			break;
 		}
+		add_size = min(em->start + em->len, page_end + 1) - cur;
 		free_extent_map(em);
 
 		if (page->index == end_index) {
@@ -527,7 +528,6 @@ static noinline int add_ra_bio_pages(struct inode *inode,
 			}
 		}
 
-		add_size = min(em->start + em->len, page_end + 1) - cur;
 		ret = bio_add_page(orig_bio, page, add_size, offset_in_page(cur));
 		if (ret != add_size) {
 			unlock_extent(tree, cur, page_end, NULL);





[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux