[PATCH 5/6] nfs: check all iov segments for correct memory access rights

Chuck Lever
2006-05-19T18:00:42Z

Add Badari's function to check access for all the segments in a passed-in
iov. We can use the total byte count later.

Signed-off-by: Chuck Lever <cel@netapp.com>
---

fs/nfs/direct.c | 65 +++++++++++++++++++++++++++++++++++--------------------
1 files changed, 41 insertions(+), 24 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 9cd6b96..3d4ded0 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -374,7 +374,6 @@ static ssize_t nfs_direct_read(struct ki
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;

- nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
rpc_clnt_sigmask(clnt, &oldset);
if (nfs_direct_read_schedule(dreq, user_addr, count, pos))
result = nfs_direct_wait(dreq);
@@ -709,8 +708,6 @@ static ssize_t nfs_direct_write(struct k
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;

- nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
-
nfs_begin_data_update(inode);

rpc_clnt_sigmask(clnt, &oldset);
@@ -721,6 +718,36 @@ static ssize_t nfs_direct_write(struct k
return result;
}

+/*
+ * Check:
+ * 1. All bytes in the user buffers are properly accessible
+ * 2. The resulting number of bytes won't overflow ssize_t
+ */
+static ssize_t check_access_ok(int type, const struct iovec *iov, unsigned long nr_segs)
+{
+ ssize_t count = 0;
+ ssize_t retval = -EINVAL;
+ unsigned long seg;
+
+ for (seg = 0; seg < nr_segs; seg++) {
+ void __user *buf = iov[seg].iov_base;
+ ssize_t len = (ssize_t) iov[seg].iov_len;
+
+ if (len < 0) /* size_t not fitting an ssize_t .. */
+ goto out;
+ if (unlikely(!access_ok(type, buf, len))) {
+ retval = -EFAULT;
+ goto out;
+ }
+ count += len;
+ if (count < 0) /* math overflow on the ssize_t */
+ goto out;
+ }
+ retval = count;
+out:
+ return retval;
+}
+
/**
* nfs_file_direct_read - file direct read operation for NFS files
* @iocb: target I/O control block
@@ -745,13 +772,18 @@ static ssize_t nfs_direct_write(struct k
ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
- ssize_t retval = -EINVAL;
+ ssize_t retval;
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
/* XXX: temporary */
const char __user *buf = iov[0].iov_base;
size_t count = iov[0].iov_len;

+ retval = check_access_ok(VERIFY_WRITE, iov, nr_segs);
+ if (retval <= 0)
+ goto out;
+ nfs_add_stats(mapping->host, NFSIOS_DIRECTREADBYTES, retval);
+
dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
file->f_dentry->d_parent->d_name.name,
file->f_dentry->d_name.name,
@@ -760,15 +792,6 @@ ssize_t nfs_file_direct_read(struct kioc
if (nr_segs != 1)
return -EINVAL;

- if (count < 0)
- goto out;
- retval = -EFAULT;
- if (!access_ok(VERIFY_WRITE, buf, count))
- goto out;
- retval = 0;
- if (!count)
- goto out;
-
retval = nfs_sync_mapping(mapping);
if (retval)
goto out;
@@ -816,6 +839,11 @@ ssize_t nfs_file_direct_write(struct kio
const char __user *buf = iov[0].iov_base;
size_t count = iov[0].iov_len;

+ retval = check_access_ok(VERIFY_READ, iov, nr_segs);
+ if (retval <= 0)
+ goto out;
+ nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, retval);
+
dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
file->f_dentry->d_parent->d_name.name,
file->f_dentry->d_name.name,
@@ -828,17 +856,6 @@ ssize_t nfs_file_direct_write(struct kio
if (retval)
goto out;

- retval = -EINVAL;
- if ((ssize_t) count < 0)
- goto out;
- retval = 0;
- if (!count)
- goto out;
-
- retval = -EFAULT;
- if (!access_ok(VERIFY_READ, buf, count))
- goto out;
-
retval = nfs_sync_mapping(mapping);
if (retval)
goto out;