jffs2: check jffs2_prealloc_raw_node_refs() result in few other places

In the Linux kernel, the following vulnerability has been resolved:

jffs2: check jffs2_prealloc_raw_node_refs() result in few other places

Fuzzing hit another invalid pointer dereference due to the lack of

checking whether jffs2_prealloc_raw_node_refs() completed successfully.

Subsequent logic implies that the node refs have been allocated.

Handle that. The code is ready for propagating the error upwards.

KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]

CPU: 1 PID: 5835 Comm: syz-executor145 Not tainted 5.10.234-syzkaller #0

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014

RIP: 0010:jffs2_link_node_ref+0xac/0x690 fs/jffs2/nodelist.c:600

Call Trace:

jffs2_mark_erased_block fs/jffs2/erase.c:460 [inline]

jffs2_erase_pending_blocks+0x688/0x1860 fs/jffs2/erase.c:118

jffs2_garbage_collect_pass+0x638/0x1a00 fs/jffs2/gc.c:253

jffs2_reserve_space+0x3f4/0xad0 fs/jffs2/nodemgmt.c:167

jffs2_write_inode_range+0x246/0xb50 fs/jffs2/write.c:362

jffs2_write_end+0x712/0x1110 fs/jffs2/file.c:302

generic_perform_write+0x2c2/0x500 mm/filemap.c:3347

__generic_file_write_iter+0x252/0x610 mm/filemap.c:3465

generic_file_write_iter+0xdb/0x230 mm/filemap.c:3497

call_write_iter include/linux/fs.h:2039 [inline]

do_iter_readv_writev+0x46d/0x750 fs/read_write.c:740

do_iter_write+0x18c/0x710 fs/read_write.c:866

vfs_writev+0x1db/0x6a0 fs/read_write.c:939

do_pwritev fs/read_write.c:1036 [inline]

__do_sys_pwritev fs/read_write.c:1083 [inline]

__se_sys_pwritev fs/read_write.c:1078 [inline]

__x64_sys_pwritev+0x235/0x310 fs/read_write.c:1078

do_syscall_64+0x30/0x40 arch/x86/entry/common.c:46

entry_SYSCALL_64_after_hwframe+0x67/0xd1

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