Re: [PATCH 1/1] ext4, dio: Remove overflow for size >2G in aio-dio code.

[Linus Torvalds <torvalds@linux-foundation.org>]

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On Sun, May 20, 2012 at 8:28 PM, manish honap
<manish_honap_vit@yahoo.co.in> wrote:
> Hello Linus,
>
> The overflow issue was seen during async dio path

Christ. fs/aio.c doesn't do the proper rw_verify_area().

As a result, it doesn't check file locks, and it doesn't seem to check
offset overflows either.

The vector versions kind of get the size limit by mistake (because
they at least use rw_copy_check_uvector(), which does limit things to
MAX_RW_COUNT), but they don't do the offset overflow check either.

Does this patch work for you? What it *should* do is the same that the
other read/write paths do (and the vector path for aio already do),
namely truncate reads or writes to MAX_RW_COUNT (which is INT_MAX
aligned down to a page).

This patch is entirely untested,

                     Linus

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 fs/aio.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 67a6db3e1b6f..e7f2fad7b4ce 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1456,6 +1456,10 @@ static ssize_t aio_setup_vectored_rw(int type, struct kiocb *kiocb, bool compat)
 	if (ret < 0)
 		goto out;
 
+	ret = rw_verify_area(type, kiocb->ki_filp, &kiocb->ki_pos, ret);
+	if (ret < 0)
+		goto out;
+
 	kiocb->ki_nr_segs = kiocb->ki_nbytes;
 	kiocb->ki_cur_seg = 0;
 	/* ki_nbytes/left now reflect bytes instead of segs */
@@ -1467,11 +1471,17 @@ out:
 	return ret;
 }
 
-static ssize_t aio_setup_single_vector(struct kiocb *kiocb)
+static ssize_t aio_setup_single_vector(int type, struct file * file, struct kiocb *kiocb)
 {
+	int bytes;
+
+	bytes = rw_verify_area(type, file, &kiocb->ki_pos, kiocb->ki_left);
+	if (bytes < 0)
+		return bytes;
+
 	kiocb->ki_iovec = &kiocb->ki_inline_vec;
 	kiocb->ki_iovec->iov_base = kiocb->ki_buf;
-	kiocb->ki_iovec->iov_len = kiocb->ki_left;
+	kiocb->ki_iovec->iov_len = bytes;
 	kiocb->ki_nr_segs = 1;
 	kiocb->ki_cur_seg = 0;
 	return 0;
@@ -1496,10 +1506,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 		if (unlikely(!access_ok(VERIFY_WRITE, kiocb->ki_buf,
 			kiocb->ki_left)))
 			break;
-		ret = security_file_permission(file, MAY_READ);
-		if (unlikely(ret))
-			break;
-		ret = aio_setup_single_vector(kiocb);
+		ret = aio_setup_single_vector(READ, file, kiocb);
 		if (ret)
 			break;
 		ret = -EINVAL;
@@ -1514,10 +1521,7 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 		if (unlikely(!access_ok(VERIFY_READ, kiocb->ki_buf,
 			kiocb->ki_left)))
 			break;
-		ret = security_file_permission(file, MAY_WRITE);
-		if (unlikely(ret))
-			break;
-		ret = aio_setup_single_vector(kiocb);
+		ret = aio_setup_single_vector(WRITE, file, kiocb);
 		if (ret)
 			break;
 		ret = -EINVAL;
@@ -1528,9 +1532,6 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 		ret = -EBADF;
 		if (unlikely(!(file->f_mode & FMODE_READ)))
 			break;
-		ret = security_file_permission(file, MAY_READ);
-		if (unlikely(ret))
-			break;
 		ret = aio_setup_vectored_rw(READ, kiocb, compat);
 		if (ret)
 			break;
@@ -1542,9 +1543,6 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat)
 		ret = -EBADF;
 		if (unlikely(!(file->f_mode & FMODE_WRITE)))
 			break;
-		ret = security_file_permission(file, MAY_WRITE);
-		if (unlikely(ret))
-			break;
 		ret = aio_setup_vectored_rw(WRITE, kiocb, compat);
 		if (ret)
 			break;