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jffs2: Fix use of uninitialized delayed_work, lockdep breakage

I've sent this one upstream.  This patch is critical if you want to run
with "prove lock correctness" (lockdep) and you happen to have certain
mtd devices.  The misuse of the uninitialized object is undefined
behaviour, but being zeroed it does not appear to have actually broken
anything other than the lockdep engine.

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
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daniel-santos authored and hauke committed Oct 19, 2018
1 parent 4bf5c43 commit 9850e4228400748dc91b07965b972279d45299d6
@@ -0,0 +1,62 @@
From a788c5272769ddbcdbab297cf386413eeac04463 Mon Sep 17 00:00:00 2001
From: Daniel Santos <daniel.santos@pobox.com>
Date: Fri, 19 Oct 2018 03:30:20 -0500
Subject: [PATCH] jffs2: Fix use of uninitialized delayed_work, lockdep
breakage

jffs2_sync_fs makes the assumption that if CONFIG_JFFS2_FS_WRITEBUFFER
is defined then a write buffer is available and has been initialized.
However, this does is not the case when the mtd device has no
out-of-band buffer:

int jffs2_nand_flash_setup(struct jffs2_sb_info *c)
{
if (!c->mtd->oobsize)
return 0;
...

The resulting call to cancel_delayed_work_sync passing a uninitialized
(but zeroed) delayed_work struct forces lockdep to become disabled.

[ 90.050639] overlayfs: upper fs does not support tmpfile.
[ 90.652264] INFO: trying to register non-static key.
[ 90.662171] the code is fine but needs lockdep annotation.
[ 90.673090] turning off the locking correctness validator.
[ 90.684021] CPU: 0 PID: 1762 Comm: mount_root Not tainted 4.14.63 #0
[ 90.696672] Stack : 00000000 00000000 80d8f6a2 00000038 805f0000 80444600 8fe364f4 805dfbe7
[ 90.713349] 80563a30 000006e2 8068370c 00000001 00000000 00000001 8e2fdc48 ffffffff
[ 90.730020] 00000000 00000000 80d90000 00000000 00000106 00000000 6465746e 312e3420
[ 90.746690] 6b636f6c 03bf0000 f8000000 20676e69 00000000 80000000 00000000 8e2c2a90
[ 90.763362] 80d90000 00000001 00000000 8e2c2a90 00000003 80260dc0 08052098 80680000
[ 90.780033] ...
[ 90.784902] Call Trace:
[ 90.789793] [<8000f0d8>] show_stack+0xb8/0x148
[ 90.798659] [<8005a000>] register_lock_class+0x270/0x55c
[ 90.809247] [<8005cb64>] __lock_acquire+0x13c/0xf7c
[ 90.818964] [<8005e314>] lock_acquire+0x194/0x1dc
[ 90.828345] [<8003f27c>] flush_work+0x200/0x24c
[ 90.837374] [<80041dfc>] __cancel_work_timer+0x158/0x210
[ 90.847958] [<801a8770>] jffs2_sync_fs+0x20/0x54
[ 90.857173] [<80125cf4>] iterate_supers+0xf4/0x120
[ 90.866729] [<80158fc4>] sys_sync+0x44/0x9c
[ 90.875067] [<80014424>] syscall_common+0x34/0x58

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
---
fs/jffs2/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -101,7 +101,8 @@ static int jffs2_sync_fs(struct super_bl
struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);

#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
- cancel_delayed_work_sync(&c->wbuf_dwork);
+ if (jffs2_is_writebuffered(c))
+ cancel_delayed_work_sync(&c->wbuf_dwork);
#endif

mutex_lock(&c->alloc_sem);
@@ -244,7 +244,7 @@ Signed-off-by: Alexandros C. Couloumbis <alex@ozo.com>
+}
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -370,14 +370,41 @@ static int __init init_jffs2_fs(void)
@@ -371,14 +371,41 @@ static int __init init_jffs2_fs(void)
BUILD_BUG_ON(sizeof(struct jffs2_raw_inode) != 68);
BUILD_BUG_ON(sizeof(struct jffs2_raw_summary) != 32);

@@ -0,0 +1,62 @@
From a788c5272769ddbcdbab297cf386413eeac04463 Mon Sep 17 00:00:00 2001
From: Daniel Santos <daniel.santos@pobox.com>
Date: Fri, 19 Oct 2018 03:30:20 -0500
Subject: [PATCH] jffs2: Fix use of uninitialized delayed_work, lockdep
breakage

jffs2_sync_fs makes the assumption that if CONFIG_JFFS2_FS_WRITEBUFFER
is defined then a write buffer is available and has been initialized.
However, this does is not the case when the mtd device has no
out-of-band buffer:

int jffs2_nand_flash_setup(struct jffs2_sb_info *c)
{
if (!c->mtd->oobsize)
return 0;
...

The resulting call to cancel_delayed_work_sync passing a uninitialized
(but zeroed) delayed_work struct forces lockdep to become disabled.

[ 90.050639] overlayfs: upper fs does not support tmpfile.
[ 90.652264] INFO: trying to register non-static key.
[ 90.662171] the code is fine but needs lockdep annotation.
[ 90.673090] turning off the locking correctness validator.
[ 90.684021] CPU: 0 PID: 1762 Comm: mount_root Not tainted 4.14.63 #0
[ 90.696672] Stack : 00000000 00000000 80d8f6a2 00000038 805f0000 80444600 8fe364f4 805dfbe7
[ 90.713349] 80563a30 000006e2 8068370c 00000001 00000000 00000001 8e2fdc48 ffffffff
[ 90.730020] 00000000 00000000 80d90000 00000000 00000106 00000000 6465746e 312e3420
[ 90.746690] 6b636f6c 03bf0000 f8000000 20676e69 00000000 80000000 00000000 8e2c2a90
[ 90.763362] 80d90000 00000001 00000000 8e2c2a90 00000003 80260dc0 08052098 80680000
[ 90.780033] ...
[ 90.784902] Call Trace:
[ 90.789793] [<8000f0d8>] show_stack+0xb8/0x148
[ 90.798659] [<8005a000>] register_lock_class+0x270/0x55c
[ 90.809247] [<8005cb64>] __lock_acquire+0x13c/0xf7c
[ 90.818964] [<8005e314>] lock_acquire+0x194/0x1dc
[ 90.828345] [<8003f27c>] flush_work+0x200/0x24c
[ 90.837374] [<80041dfc>] __cancel_work_timer+0x158/0x210
[ 90.847958] [<801a8770>] jffs2_sync_fs+0x20/0x54
[ 90.857173] [<80125cf4>] iterate_supers+0xf4/0x120
[ 90.866729] [<80158fc4>] sys_sync+0x44/0x9c
[ 90.875067] [<80014424>] syscall_common+0x34/0x58

Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Reviewed-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
---
fs/jffs2/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -101,7 +101,8 @@ static int jffs2_sync_fs(struct super_bl
struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);

#ifdef CONFIG_JFFS2_FS_WRITEBUFFER
- cancel_delayed_work_sync(&c->wbuf_dwork);
+ if (jffs2_is_writebuffered(c))
+ cancel_delayed_work_sync(&c->wbuf_dwork);
#endif

mutex_lock(&c->alloc_sem);
@@ -244,7 +244,7 @@ Signed-off-by: Alexandros C. Couloumbis <alex@ozo.com>
+}
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -370,14 +370,41 @@ static int __init init_jffs2_fs(void)
@@ -371,14 +371,41 @@ static int __init init_jffs2_fs(void)
BUILD_BUG_ON(sizeof(struct jffs2_raw_inode) != 68);
BUILD_BUG_ON(sizeof(struct jffs2_raw_summary) != 32);

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