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Subject[PATCH] eCryptfs: Fix kernel bug for writing mmaped non-eCryptfs file
Date
eCryptfs did not handle the writing for mmaped non-eCryptfs file.
Instead, it put BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED))
on ecryptfs_writepage call path. This patch enables eCryptfs to
deal with such case, to fully support non-eCryptfs operations as it
claims.

---
To make the bug present

cd cipher // enter eCryptfs cipher text folder
echo "123" > foo // make non-eCryptfs file
cd ..
mount -t ecryptfs cipher plain -o ecryptfs_passthrough // allow for non-eCryptfs files to be read and written from within an eCryptfs mount
cd plain
run the following program
int main()
{
int fd = open("foo", O_RDWR);
char * addr;
addr = (char *)mmap(NULL, 256, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
add[0] = '3';
munmap(addr, 256);
close(fd);
return 0;
}
Signed-off-by: Li Wang <liwang@nudt.edu.cn>
Signed-off-by: Yunchuan Wen <wenyunchuan@kylinos.com.cn>
---
fs/ecryptfs/mmap.c | 26 ++++++++++++++++++++++++++
1 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 10ec695..a4be0e9 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -65,6 +65,32 @@ struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
{
int rc;
+ struct inode *inode;
+ struct ecryptfs_crypt_stat *crypt_stat;
+
+ inode = page->mapping->host;
+ crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
+ if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
+ size_t size;
+ loff_t file_size = i_size_read(inode);
+ pgoff_t end_page_index = file_size >> PAGE_CACHE_SHIFT;
+
+ if (end_page_index < page->index)
+ size = 0;
+ else if (end_page_index == page->index)
+ size = file_size & ~PAGE_CACHE_MASK;
+ else
+ size = PAGE_CACHE_SIZE;
+
+ rc = ecryptfs_write_lower_page_segment(inode, page, 0, size);
+ if (unlikely(rc)) {
+ ecryptfs_printk(KERN_WARNING, "Error write "
+ "page (upper index [0x%.16lx])\n", page->index);
+ ClearPageUptodate(page);
+ } else
+ SetPageUptodate(page);
+ goto out;
+ }

/*
* Refuse to write the page out if we are called from reclaim context
--
1.7.6.5


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