The patch titled Subject: nilfs2: fix leak of nilfs_root in case of writer thread creation failure has been added to the -mm mm-hotfixes-unstable branch. Its filename is nilfs2-fix-leak-of-nilfs_root-in-case-of-writer-thread-creation-failure.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Ryusuke Konishi konishi.ryusuke@gmail.com Subject: nilfs2: fix leak of nilfs_root in case of writer thread creation failure Date: Fri, 7 Oct 2022 17:52:26 +0900

If nilfs_attach_log_writer() failed to create a log writer thread, it frees a data structure of the log writer without any cleanup. After commit e912a5b66837 ("nilfs2: use root object to get ifile"), this causes a leak of struct nilfs_root, which started to leak an ifile metadata inode and a kobject on that struct.

In addition, if the kernel is booted with panic_on_warn, the above ifile metadata inode leak will cause the following panic when the nilfs2 kernel module is removed:

kmem_cache_destroy nilfs2_inode_cache: Slab cache still has objects when called from nilfs_destroy_cachep+0x16/0x3a [nilfs2] WARNING: CPU: 8 PID: 1464 at mm/slab_common.c:494 kmem_cache_destroy+0x138/0x140 ... RIP: 0010:kmem_cache_destroy+0x138/0x140 Code: 00 20 00 00 e8 a9 55 d8 ff e9 76 ff ff ff 48 8b 53 60 48 c7 c6 20 70 65 86 48 c7 c7 d8 69 9c 86 48 8b 4c 24 28 e8 ef 71 c7 00 <0f> 0b e9 53 ff ff ff c3 48 81 ff ff 0f 00 00 77 03 31 c0 c3 53 48 ... Call Trace: <TASK> ? nilfs_palloc_freev.cold.24+0x58/0x58 [nilfs2] nilfs_destroy_cachep+0x16/0x3a [nilfs2] exit_nilfs_fs+0xa/0x1b [nilfs2] __x64_sys_delete_module+0x1d9/0x3a0 ? __sanitizer_cov_trace_pc+0x1a/0x50 ? syscall_trace_enter.isra.19+0x119/0x190 do_syscall_64+0x34/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd ... </TASK> Kernel panic - not syncing: panic_on_warn set ...

This patch fixes these issues by calling nilfs_detach_log_writer() cleanup function if spawning the log writer thread fails.

Link: https://lkml.kernel.org/r/20221007085226.57667-1-konishi.ryusuke@gmail.com Fixes: e912a5b66837 ("nilfs2: use root object to get ifile") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+7381dc4ad60658ca4c05@syzkaller.appspotmail.com Tested-by: Ryusuke Konishi konishi.ryusuke@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/nilfs2/segment.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/fs/nilfs2/segment.c~nilfs2-fix-leak-of-nilfs_root-in-case-of-writer-thread-creation-failure +++ a/fs/nilfs2/segment.c @@ -2786,10 +2786,9 @@ int nilfs_attach_log_writer(struct super inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);

err = nilfs_segctor_start_thread(nilfs->ns_writer); - if (err) { - kfree(nilfs->ns_writer); - nilfs->ns_writer = NULL; - } + if (unlikely(err)) + nilfs_detach_log_writer(sb); + return err; }

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Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-fix-use-after-free-bug-of-struct-nilfs_root.patch nilfs2-fix-null-pointer-dereference-at-nilfs_bmap_lookup_at_level.patch nilfs2-fix-leak-of-nilfs_root-in-case-of-writer-thread-creation-failure.patch nilfs2-replace-warn_ons-by-nilfs_error-for-checkpoint-acquisition-failure.patch