LKML Archive on
help / color / mirror / Atom feed
* [PATCH] vfs: read file_handle only once in handle_to_path
@ 2015-01-27 16:58 Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2015-01-27 16:58 UTC (permalink / raw)
  To: linux-kernel; +Cc: Sasha Levin, Alexander Viro, linux-fsdevel

We used to read file_handle twice. Once to get the amount of extra bytes, and
once to fetch the entire structure.

This may be problematic since we do size verifications only after the first
read, so if the number of extra bytes changes in userspace between the first
and second calls, we'll have an incoherent view of file_handle.

Instead, read the constant size once, and copy that over to the final
structure without having to re-read it again.

Signed-off-by: Sasha Levin <>
 fs/fhandle.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/fhandle.c b/fs/fhandle.c
index 999ff5c..f26d0e1 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -195,8 +195,9 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
 		goto out_err;
 	/* copy the full handle */
-	if (copy_from_user(handle, ufh,
-			   sizeof(struct file_handle) +
+	*handle = f_handle;
+	if (copy_from_user(handle + sizeof(struct file_handle),
+			   ufh + sizeof(struct file_handle),
 			   f_handle.handle_bytes)) {
 		retval = -EFAULT;
 		goto out_handle;

^ permalink raw reply	[flat|nested] only message in thread

only message in thread, other threads:[~2015-01-27 16:59 UTC | newest]

Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-01-27 16:58 [PATCH] vfs: read file_handle only once in handle_to_path Sasha Levin

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).