2013-01-23 12:56:17

by Jan Kara

Subject: [PATCH 1/4] ext4: Fix possible use-after-free with AIO

Running AIO is pinning inode in memory using file reference. Once AIO
is completed using aio_complete(), file reference is put and inode can
be freed from memory. So we have to be sure that calling aio_complete()
is the last thing we do with the inode.

CC: [email protected]
CC: "Theodore Ts'o" <[email protected]>
CC: [email protected]
Signed-off-by: Jan Kara <[email protected]>
---
fs/ext4/inode.c | 2 +-
fs/ext4/page-io.c | 9 ++++-----
2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index cbfe13b..ba06638 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2977,9 +2977,9 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
ext4_free_io_end(io_end);
out:
+ inode_dio_done(inode);
if (is_async)
aio_complete(iocb, ret, 0);
- inode_dio_done(inode);
return;
}

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 0016fbc..b42d04f 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -103,14 +103,13 @@ static int ext4_end_io(ext4_io_end_t *io)
"(inode %lu, offset %llu, size %zd, error %d)",
inode->i_ino, offset, size, ret);
}
- if (io->iocb)
- aio_complete(io->iocb, io->result, 0);
-
- if (io->flag & EXT4_IO_END_DIRECT)
- inode_dio_done(inode);
/* Wake up anyone waiting on unwritten extent conversion */
if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
wake_up_all(ext4_ioend_wq(inode));
+ if (io->flag & EXT4_IO_END_DIRECT)
+ inode_dio_done(inode);
+ if (io->iocb)
+ aio_complete(io->iocb, io->result, 0);
return ret;
}

--
1.7.1

2013-01-23 13:18:10

by Carlos Maiolino

Subject: Re: [PATCH 1/4] ext4: Fix possible use-after-free with AIO

Looks Good,

Reviewed-by: Carlos Maiolino <[email protected]>
On Wed, Jan 23, 2013 at 01:56:17PM +0100, Jan Kara wrote:
> Running AIO is pinning inode in memory using file reference. Once AIO
> is completed using aio_complete(), file reference is put and inode can
> be freed from memory. So we have to be sure that calling aio_complete()
> is the last thing we do with the inode.
>
> CC: [email protected]
> CC: "Theodore Ts'o" <[email protected]>
> CC: [email protected]
> Signed-off-by: Jan Kara <[email protected]>
> ---
> fs/ext4/inode.c | 2 +-
> fs/ext4/page-io.c | 9 ++++-----
> 2 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index cbfe13b..ba06638 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2977,9 +2977,9 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
> if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
> ext4_free_io_end(io_end);
> out:
> + inode_dio_done(inode);
> if (is_async)
> aio_complete(iocb, ret, 0);
> - inode_dio_done(inode);
> return;
> }
>
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 0016fbc..b42d04f 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -103,14 +103,13 @@ static int ext4_end_io(ext4_io_end_t *io)
> "(inode %lu, offset %llu, size %zd, error %d)",
> inode->i_ino, offset, size, ret);
> }
> - if (io->iocb)
> - aio_complete(io->iocb, io->result, 0);
> -
> - if (io->flag & EXT4_IO_END_DIRECT)
> - inode_dio_done(inode);
> /* Wake up anyone waiting on unwritten extent conversion */
> if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
> wake_up_all(ext4_ioend_wq(inode));
> + if (io->flag & EXT4_IO_END_DIRECT)
> + inode_dio_done(inode);
> + if (io->iocb)
> + aio_complete(io->iocb, io->result, 0);
> return ret;
> }
>
> --
> 1.7.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html

--
Carlos