[PATCH 6.4 744/800] jffs2: reduce stack usage in jffs2_build_xattr_subsystem()

Greg Kroah-Hartman
2023-07-16T20:27:40Z

From: Fabian Frederick <fabf@skynet.be>

commit 1168f095417643f663caa341211e117db552989f upstream.

Use kcalloc() for allocation/flush of 128 pointers table to
reduce stack usage.

Function now returns -ENOMEM or 0 on success.

stackusage
Before:
./fs/jffs2/xattr.c:775 jffs2_build_xattr_subsystem 1208
dynamic,bounded

After:
./fs/jffs2/xattr.c:775 jffs2_build_xattr_subsystem 192
dynamic,bounded

Also update definition when CONFIG_JFFS2_FS_XATTR is not enabled

Tested with an MTD mount point and some user set/getfattr.

Many current target on OpenWRT also suffer from a compilation warning
(that become an error with CONFIG_WERROR) with the following output:

fs/jffs2/xattr.c: In function 'jffs2_build_xattr_subsystem':
fs/jffs2/xattr.c:887:1: error: the frame size of 1088 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
887 | }
| ^

Using dynamic allocation fix this compilation warning.

Fixes: c9f700f840bd ("[JFFS2][XATTR] using 'delete marker' for xdatum/xref deletion")
Reported-by: Tim Gardner <tim.gardner@canonical.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Ron Economos <re@w6rz.net>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Cc: stable@vger.kernel.org
Message-Id: <20230506045612.16616-1-ansuelsmth@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/jffs2/build.c | 5 ++++-
fs/jffs2/xattr.c | 13 +++++++++----
fs/jffs2/xattr.h | 4 ++--
3 files changed, 15 insertions(+), 7 deletions(-)

--- a/fs/jffs2/build.c
+++ b/fs/jffs2/build.c
@@ -211,7 +211,10 @@ static int jffs2_build_filesystem(struct
ic->scan_dents = NULL;
cond_resched();
}
- jffs2_build_xattr_subsystem(c);
+ ret = jffs2_build_xattr_subsystem(c);
+ if (ret)
+ goto exit;
+
c->flags &= ~JFFS2_SB_FLAG_BUILDING;

dbg_fsbuild("FS build complete\n");
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -772,10 +772,10 @@ void jffs2_clear_xattr_subsystem(struct
}

#define XREF_TMPHASH_SIZE (128)
-void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
+int 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 +784,12 @@ void jffs2_build_xattr_subsystem(struct

BUG_ON(!(c->flags & JFFS2_SB_FLAG_BUILDING));

+ xref_tmphash = kcalloc(XREF_TMPHASH_SIZE,
+ sizeof(struct jffs2_xattr_ref *), GFP_KERNEL);
+ if (!xref_tmphash)
+ return -ENOMEM;
+
/* 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 +887,8 @@ void jffs2_build_xattr_subsystem(struct
"%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);
+ return 0;
}

struct jffs2_xattr_datum *jffs2_setup_xattr_datum(struct jffs2_sb_info *c,
--- a/fs/jffs2/xattr.h
+++ b/fs/jffs2/xattr.h
@@ -71,7 +71,7 @@ static inline int is_xattr_ref_dead(stru
#ifdef CONFIG_JFFS2_FS_XATTR

extern void jffs2_init_xattr_subsystem(struct jffs2_sb_info *c);
-extern void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c);
+extern int jffs2_build_xattr_subsystem(struct jffs2_sb_info *c);
extern void jffs2_clear_xattr_subsystem(struct jffs2_sb_info *c);

extern struct jffs2_xattr_datum *jffs2_setup_xattr_datum(struct jffs2_sb_info *c,
@@ -103,7 +103,7 @@ extern ssize_t jffs2_listxattr(struct de
#else

#define jffs2_init_xattr_subsystem(c)
-#define jffs2_build_xattr_subsystem(c)
+#define jffs2_build_xattr_subsystem(c) (0)
#define jffs2_clear_xattr_subsystem(c)

#define jffs2_xattr_do_crccheck_inode(c, ic)