[PATCH] ext4: disable retry logic in ext4_set_encrypted_filename

[PATCH] ext4: disable retry logic in ext4_set_encrypted_filename

[Arnd Bergmann]

gcc correctly warns that the ctx variable in ext4_set_encrypted_filename
has gone out of scope in ext4_set_encrypted_filename if we enter the
retry path and a 'goto' into the previous code block can not guarantee
to get the contents back:

fs/ext4/namei.c: In function 'ext4_set_encrypted_filename':
fs/ext4/namei.c:4035:10: warning: 'ctx' may be used uninitialized in this function [-Wmaybe-uninitialized]
   retval = ext4_xattr_set_handle(handle, inode,

I tried moving the variable declaration to the start of the function,
but that does not shut up the warning, as it's apparently too hard
for the compiler to follow the control flow and determine that it's
correct (or for me reading the code, for that matter).

This adds a hack to avoid the undefined behavior at the cost of
losing the chance to retry on a spurious -ENOSPC error. We probably
need a better solution.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 374431bae296 ("ext4 crypto: add ioctls to allow backup of encryption metadata")
---
The warning appeared with next-20121231, which is the latest next release,
nevermind if it has already been fixed in the meantime.

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index c03f310200d6..fd2bd090bdfa 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -4113,7 +4113,7 @@ out:
 	}
 	if (handle)
 		ext4_journal_stop(handle);
-	if (do_retry) {
+	if (do_retry /* FIXME: ctx is invalid */ && 0) {
 		do_retry = 0;
 		goto retry;
 	}

Re: [PATCH] ext4: disable retry logic in ext4_set_encrypted_filename

[Theodore Ts'o]

On Sat, Jan 02, 2016 at 08:50:11PM +0100, Arnd Bergmann wrote:
> gcc correctly warns that the ctx variable in ext4_set_encrypted_filename
> has gone out of scope in ext4_set_encrypted_filename if we enter the
> retry path and a 'goto' into the previous code block can not guarantee
> to get the contents back:
> 
> fs/ext4/namei.c: In function 'ext4_set_encrypted_filename':
> fs/ext4/namei.c:4035:10: warning: 'ctx' may be used uninitialized in this function [-Wmaybe-uninitialized]
>    retval = ext4_xattr_set_handle(handle, inode,

Sorry, this was a known bug that I fixed about a week ago, but I
hadn't pushed out an update to the ext4 dev branch because I hadn't
had a chance to finish testing the project quota changes.  I've just
pushed out an update.

					- Ted