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    SubjectRe: [PATCH] eCryptfs: infinite loop bug
    On 2012-01-18 23:26:52, Cong Wang wrote:
    > On 01/18/2012 03:30 PM, Li Wang wrote:
    > >Hi,
    > > There is an infinite loop bug in eCryptfs, to make it present,
    > >just truncate to generate a huge file (>= 4G) on a 32-bit machine
    > >under the plain text foleder mounted with eCryptfs, a simple command
    > >'truncate -s 4G dummy' is enough. Note: 4GB is smaller than 4G,
    > >therefore the following command 'truncate -s 4GB dummy' will not trigger this bug.
    > >The bug comes from a data overflow, the patch below fixes it.
    > >
    > >
    >
    > Hi,
    >
    > Your patch is not correctly generated, you need to make the diff on
    > top of the source tree.
    >
    > Also, after reviewing the code, I think there are more places need
    > to fix. Can you try my patch below?

    Thanks for the review and additional fixes. See my comments below.

    >
    > Thanks.
    >
    > ---->
    >
    > Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
    >
    >

    > diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
    > index a9f29b1..9ca9c17 100644
    > --- a/fs/ecryptfs/ecryptfs_kernel.h
    > +++ b/fs/ecryptfs/ecryptfs_kernel.h
    > @@ -653,7 +653,7 @@ int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
    > loff_t offset, size_t size);
    > int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
    > struct page *page_for_lower,
    > - size_t offset_in_page, size_t size);
    > + loff_t offset_in_page, size_t size);
    > int ecryptfs_write(struct inode *inode, char *data, loff_t offset, size_t size);
    > int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
    > struct inode *ecryptfs_inode);
    > diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c
    > index 3745f7c..93d80c4 100644
    > --- a/fs/ecryptfs/read_write.c
    > +++ b/fs/ecryptfs/read_write.c
    > @@ -72,7 +72,7 @@ int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
    > */
    > int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
    > struct page *page_for_lower,
    > - size_t offset_in_page, size_t size)
    > + loff_t offset_in_page, size_t size)

    mm/filemap.c uses unsigned long for variables used to identify an offset
    into a single page. That's what I'm tempted to use for offset_in_page,
    rather than loff_t.

    > {
    > char *virt;
    > loff_t offset;
    > @@ -128,15 +128,15 @@ int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
    > pos = offset;
    > while (pos < (offset + size)) {
    > pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
    > - size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
    > - size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
    > - size_t total_remaining_bytes = ((offset + size) - pos);
    > + loff_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
    > + loff_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);

    unsigned long should work for start_offset_in_page and num_bytes, too.

    Tyler

    > + loff_t total_remaining_bytes = ((offset + size) - pos);
    >
    > if (num_bytes > total_remaining_bytes)
    > num_bytes = total_remaining_bytes;
    > if (pos < offset) {
    > /* remaining zeros to write, up to destination offset */
    > - size_t total_remaining_zeros = (offset - pos);
    > + loff_t total_remaining_zeros = (offset - pos);
    >
    > if (num_bytes > total_remaining_zeros)
    > num_bytes = total_remaining_zeros;

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