Ocfs2 devel - Aug 2014 - [patch 01/10] ocfs2: do not write error flag to user structure we cannot copy from/to

From: Ben Hutchings <ben at decadent.org.uk>
Subject: ocfs2: do not write error flag to user structure we cannot copy from/to

If we failed to copy from the structure, writing back the flags leaks 31
bits of kernel memory (the rest of the ir_flags field).

In any case, if we cannot copy from/to the structure, why should we expect
putting just the flags to work?

Also make sure ocfs2_info_handle_freeinode() returns the right error code
if the copy_to_user() fails.

Fixes: ddee5cdb70e6 ('Ocfs2: Add new OCFS2_IOC_INFO ioctl for ocfs2
v8.')
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Mark Fasheh <mfasheh at suse.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 fs/ocfs2/ioctl.c |  129 +++++++++++++++------------------------------
 1 file changed, 43 insertions(+), 86 deletions(-)

diff -puN
fs/ocfs2/ioctl.c~ocfs2-do-not-write-error-flag-to-user-structure-we-cannot-copy-from-to
fs/ocfs2/ioctl.c
---
a/fs/ocfs2/ioctl.c~ocfs2-do-not-write-error-flag-to-user-structure-we-cannot-copy-from-to
+++ a/fs/ocfs2/ioctl.c
@@ -35,9 +35,8 @@
 		copy_to_user((typeof(a) __user *)b, &(a), sizeof(a))
 
 /*
- * This call is void because we are already reporting an error that may
- * be -EFAULT.  The error will be returned from the ioctl(2) call.  It's
- * just a best-effort to tell userspace that this request caused the error.
+ * This is just a best-effort to tell userspace that this request
+ * caused the error.
  */
 static inline void o2info_set_request_error(struct ocfs2_info_request *kreq,
 					struct ocfs2_info_request __user *req)
@@ -146,136 +145,105 @@ bail:
 static int ocfs2_info_handle_blocksize(struct inode *inode,
 				       struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_blocksize oib;
 
 	if (o2info_from_user(oib, req))
-		goto bail;
+		return -EFAULT;
 
 	oib.ib_blocksize = inode->i_sb->s_blocksize;
 
 	o2info_set_request_filled(&oib.ib_req);
 
 	if (o2info_to_user(oib, req))
-		goto bail;
+		return -EFAULT;
 
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oib.ib_req, req);
-
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_clustersize(struct inode *inode,
 					 struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_clustersize oic;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oic, req))
-		goto bail;
+		return -EFAULT;
 
 	oic.ic_clustersize = osb->s_clustersize;
 
 	o2info_set_request_filled(&oic.ic_req);
 
 	if (o2info_to_user(oic, req))
-		goto bail;
+		return -EFAULT;
 
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oic.ic_req, req);
-
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_maxslots(struct inode *inode,
 				      struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_maxslots oim;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oim, req))
-		goto bail;
+		return -EFAULT;
 
 	oim.im_max_slots = osb->max_slots;
 
 	o2info_set_request_filled(&oim.im_req);
 
 	if (o2info_to_user(oim, req))
-		goto bail;
-
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oim.im_req, req);
+		return -EFAULT;
 
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_label(struct inode *inode,
 				   struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_label oil;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oil, req))
-		goto bail;
+		return -EFAULT;
 
 	memcpy(oil.il_label, osb->vol_label, OCFS2_MAX_VOL_LABEL_LEN);
 
 	o2info_set_request_filled(&oil.il_req);
 
 	if (o2info_to_user(oil, req))
-		goto bail;
+		return -EFAULT;
 
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oil.il_req, req);
-
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_uuid(struct inode *inode,
 				  struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_uuid oiu;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oiu, req))
-		goto bail;
+		return -EFAULT;
 
 	memcpy(oiu.iu_uuid_str, osb->uuid_str, OCFS2_TEXT_UUID_LEN + 1);
 
 	o2info_set_request_filled(&oiu.iu_req);
 
 	if (o2info_to_user(oiu, req))
-		goto bail;
-
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oiu.iu_req, req);
+		return -EFAULT;
 
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_fs_features(struct inode *inode,
 					 struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_fs_features oif;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oif, req))
-		goto bail;
+		return -EFAULT;
 
 	oif.if_compat_features = osb->s_feature_compat;
 	oif.if_incompat_features = osb->s_feature_incompat;
@@ -284,39 +252,28 @@ static int ocfs2_info_handle_fs_features
 	o2info_set_request_filled(&oif.if_req);
 
 	if (o2info_to_user(oif, req))
-		goto bail;
+		return -EFAULT;
 
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oif.if_req, req);
-
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_handle_journal_size(struct inode *inode,
 					  struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_journal_size oij;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 
 	if (o2info_from_user(oij, req))
-		goto bail;
+		return -EFAULT;
 
 	oij.ij_journal_size = i_size_read(osb->journal->j_inode);
 
 	o2info_set_request_filled(&oij.ij_req);
 
 	if (o2info_to_user(oij, req))
-		goto bail;
-
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oij.ij_req, req);
+		return -EFAULT;
 
-	return status;
+	return 0;
 }
 
 static int ocfs2_info_scan_inode_alloc(struct ocfs2_super *osb,
@@ -373,7 +330,7 @@ static int ocfs2_info_handle_freeinode(s
 	u32 i;
 	u64 blkno = -1;
 	char namebuf[40];
-	int status = -EFAULT, type = INODE_ALLOC_SYSTEM_INODE;
+	int status, type = INODE_ALLOC_SYSTEM_INODE;
 	struct ocfs2_info_freeinode *oifi = NULL;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 	struct inode *inode_alloc = NULL;
@@ -385,8 +342,10 @@ static int ocfs2_info_handle_freeinode(s
 		goto out_err;
 	}
 
-	if (o2info_from_user(*oifi, req))
-		goto bail;
+	if (o2info_from_user(*oifi, req)) {
+		status = -EFAULT;
+		goto out_free;
+	}
 
 	oifi->ifi_slotnum = osb->max_slots;
 
@@ -424,14 +383,16 @@ static int ocfs2_info_handle_freeinode(s
 
 	o2info_set_request_filled(&oifi->ifi_req);
 
-	if (o2info_to_user(*oifi, req))
-		goto bail;
+	if (o2info_to_user(*oifi, req)) {
+		status = -EFAULT;
+		goto out_free;
+	}
 
 	status = 0;
 bail:
 	if (status)
 		o2info_set_request_error(&oifi->ifi_req, req);
-
+out_free:
 	kfree(oifi);
 out_err:
 	return status;
@@ -658,7 +619,7 @@ static int ocfs2_info_handle_freefrag(st
 {
 	u64 blkno = -1;
 	char namebuf[40];
-	int status = -EFAULT, type = GLOBAL_BITMAP_SYSTEM_INODE;
+	int status, type = GLOBAL_BITMAP_SYSTEM_INODE;
 
 	struct ocfs2_info_freefrag *oiff;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
@@ -671,8 +632,10 @@ static int ocfs2_info_handle_freefrag(st
 		goto out_err;
 	}
 
-	if (o2info_from_user(*oiff, req))
-		goto bail;
+	if (o2info_from_user(*oiff, req)) {
+		status = -EFAULT;
+		goto out_free;
+	}
 	/*
 	 * chunksize from userspace should be power of 2.
 	 */
@@ -711,14 +674,14 @@ static int ocfs2_info_handle_freefrag(st
 
 	if (o2info_to_user(*oiff, req)) {
 		status = -EFAULT;
-		goto bail;
+		goto out_free;
 	}
 
 	status = 0;
 bail:
 	if (status)
 		o2info_set_request_error(&oiff->iff_req, req);
-
+out_free:
 	kfree(oiff);
 out_err:
 	return status;
@@ -727,23 +690,17 @@ out_err:
 static int ocfs2_info_handle_unknown(struct inode *inode,
 				     struct ocfs2_info_request __user *req)
 {
-	int status = -EFAULT;
 	struct ocfs2_info_request oir;
 
 	if (o2info_from_user(oir, req))
-		goto bail;
+		return -EFAULT;
 
 	o2info_clear_request_filled(&oir);
 
 	if (o2info_to_user(oir, req))
-		goto bail;
-
-	status = 0;
-bail:
-	if (status)
-		o2info_set_request_error(&oir, req);
+		return -EFAULT;
 
-	return status;
+	return 0;
 }
 
 /*
_

On Wed, Aug 06, 2014 at 01:32:00PM -0700, Andrew Morton
wrote:
> From: Ben Hutchings <ben at decadent.org.uk>
> Subject: ocfs2: do not write error flag to user structure we cannot copy
from/to
> 
> If we failed to copy from the structure, writing back the flags leaks 31
> bits of kernel memory (the rest of the ir_flags field).
> 
> In any case, if we cannot copy from/to the structure, why should we expect
> putting just the flags to work?
> 
> Also make sure ocfs2_info_handle_freeinode() returns the right error code
> if the copy_to_user() fails.
> 
> Fixes: ddee5cdb70e6 ('Ocfs2: Add new OCFS2_IOC_INFO ioctl for ocfs2
v8.')
> Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
> Cc: Joel Becker <jlbec at evilplan.org>
> Cc: Mark Fasheh <mfasheh at suse.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>

This looks good, thanks Ben!

Reviewed-by: Mark Fasheh <mfasheh at suse.de>
	--Mark

--
Mark Fasheh