[PATCH 2/2] jffs2: initialize inocache earlier

[Fedor Pchelkin]

Inside jffs2_new_inode() there is a small gap when jffs2_init_acl_pre() or
jffs2_do_new_inode() may fail e.g. due to a memory allocation error while
uninit inocache field is touched upon subsequent inode eviction.

general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
CPU: 0 PID: 10592 Comm: syz-executor.1 Not tainted 5.10.209-syzkaller #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:jffs2_xattr_delete_inode+0x35/0x130 fs/jffs2/xattr.c:602
Call Trace:
 jffs2_do_clear_inode+0x4c/0x570 fs/jffs2/readinode.c:1418
 evict+0x281/0x6b0 fs/inode.c:577
 iput_final fs/inode.c:1697 [inline]
 iput.part.0+0x4df/0x6d0 fs/inode.c:1723
 iput+0x58/0x80 fs/inode.c:1713
 jffs2_new_inode+0xb12/0xdb0 fs/jffs2/fs.c:469
 jffs2_create+0x90/0x400 fs/jffs2/dir.c:177
 lookup_open.isra.0+0xead/0x1260 fs/namei.c:3169
 open_last_lookups fs/namei.c:3239 [inline]
 path_openat+0x96c/0x2670 fs/namei.c:3428
 do_filp_open+0x1a4/0x3f0 fs/namei.c:3458
 do_sys_openat2+0x171/0x420 fs/open.c:1186
 do_sys_open fs/open.c:1202 [inline]
 __do_sys_openat fs/open.c:1218 [inline]
 __se_sys_openat fs/open.c:1213 [inline]
 __x64_sys_openat+0x13c/0x1f0 fs/open.c:1213
 do_syscall_64+0x30/0x40 arch/x86/entry/common.c:46

Initialize the inocache pointer to a NULL value while preparing an inode
in jffs2_init_inode_info(). jffs2_xattr_delete_inode() will handle it
later just fine.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable at vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
---
 fs/jffs2/os-linux.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/jffs2/os-linux.h b/fs/jffs2/os-linux.h
index 86ab014a349c..39b6565f10c9 100644
--- a/fs/jffs2/os-linux.h
+++ b/fs/jffs2/os-linux.h
@@ -55,6 +55,7 @@ static inline void jffs2_init_inode_info(struct jffs2_inode_info *f)
 	f->metadata = NULL;
 	f->dents = NULL;
 	f->target = NULL;
+	f->inocache = NULL;
 	f->flags = 0;
 	f->usercompr = 0;
 }
-- 
2.39.5