[PATCH v4.4-rc8] jffs2: xattr: Silence frame size warning

[PATCH v4.4-rc8] jffs2: xattr: Silence frame size warning

[tim.gardner]

From: Tim Gardner <tim.gardner@canonical.com>

fs/jffs2/xattr.c: In function 'jffs2_build_xattr_subsystem':
fs/jffs2/xattr.c:887:1: warning: the frame size of 1128 bytes is larger than 1024 bytes [-Wframe-larger-than=]
 }

gcc version 5.3.1 20151219 (Ubuntu 5.3.1-4ubuntu1)

Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 fs/jffs2/xattr.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 4c2c036..160ddcd 100644
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -775,7 +775,7 @@ void jffs2_clear_xattr_subsystem(struct jffs2_sb_info *c)
 void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
 {
 	struct jffs2_xattr_ref *ref, *_ref;
-	struct jffs2_xattr_ref *xref_tmphash[XREF_TMPHASH_SIZE];
+	struct jffs2_xattr_ref **xref_tmphash;
 	struct jffs2_xattr_datum *xd, *_xd;
 	struct jffs2_inode_cache *ic;
 	struct jffs2_raw_node_ref *raw;
@@ -784,9 +784,14 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
 
 	BUG_ON(!(c->flags & JFFS2_SB_FLAG_BUILDING));
 
+	xref_tmphash = kcalloc(XREF_TMPHASH_SIZE, sizeof(*xref_tmphash),
+		GFP_KERNEL);
+	if (!xref_tmphash) {
+		JFFS2_WARNING("kcalloc failure\n");
+		return;
+	}
+
 	/* Phase.1 : Merge same xref */
-	for (i=0; i < XREF_TMPHASH_SIZE; i++)
-		xref_tmphash[i] = NULL;
 	for (ref=c->xref_temp; ref; ref=_ref) {
 		struct jffs2_xattr_ref *tmp;
 
@@ -884,6 +889,7 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
 		     "%u of xref (%u dead, %u orphan) found.\n",
 		     xdatum_count, xdatum_unchecked_count, xdatum_orphan_count,
 		     xref_count, xref_dead_count, xref_orphan_count);
+	kfree(xref_tmphash);
 }
 
 struct jffs2_xattr_datum *jffs2_setup_xattr_datum(struct jffs2_sb_info *c,
-- 
1.9.1

Re: [PATCH v4.4-rc8] jffs2: xattr: Silence frame size warning

[David Woodhouse]

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On Thu, 2016-01-07 at 12:11 -0700, tim.gardner@canonical.com wrote:
> From: Tim Gardner <tim.gardner@canonical.com>
> 
> fs/jffs2/xattr.c: In function 'jffs2_build_xattr_subsystem':
> fs/jffs2/xattr.c:887:1: warning: the frame size of 1128 bytes is
> larger than 1024 bytes [-Wframe-larger-than=]
>  }

At first glance, that looks like it's just bypassing the entire
contents of that function if the allocation fails, leaving the various
data structures in an inconsistent state and raw node refs unchecked,
which will lead to lots of issues later once the mount has completed
and GC can never get unstuck.

So at the very least, your commit message is lacking the explanation of
what the implications are, and *why* you have satisfied yourself that
it's actually OK.

At worst, the patch is entirely broken.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@intel.com                              Intel Corporation


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