From: Nanyong Sun <sunnanyong@xxxxxxxxxx> Subject: nilfs2: fix memory leak in nilfs_sysfs_create_device_group Patch series "nilfs2: fix incorrect usage of kobject". This patchset from Nanyong Sun fixes memory leak issues and a NULL pointer dereference issue caused by incorrect usage of kboject in nilfs2 sysfs implementation. This patch (of 6): Reported by syzkaller: BUG: memory leak unreferenced object 0xffff888100ca8988 (size 8): comm "syz-executor.1", pid 1930, jiffies 4294745569 (age 18.052s) hex dump (first 8 bytes): 6c 6f 6f 70 31 00 ff ff loop1... backtrace: [<000000009d9e0ac4>] slab_alloc_node mm/slub.c:2972 [inline] [<000000009d9e0ac4>] slab_alloc mm/slub.c:2980 [inline] [<000000009d9e0ac4>] __kmalloc_track_caller+0x164/0x330 mm/slub.c:4644 [<00000000b1825477>] kstrdup+0x36/0x70 mm/util.c:60 [<00000000fa081499>] kstrdup_const+0x35/0x60 mm/util.c:83 [<0000000024d13570>] kvasprintf_const+0xf1/0x180 lib/kasprintf.c:48 [<0000000024b69715>] kobject_set_name_vargs+0x56/0x150 lib/kobject.c:289 [<000000003fedac3d>] kobject_add_varg lib/kobject.c:384 [inline] [<000000003fedac3d>] kobject_init_and_add+0xc9/0x150 lib/kobject.c:473 [<000000002795bd99>] nilfs_sysfs_create_device_group+0x150/0x7d0 fs/nilfs2/sysfs.c:986 [<00000000567fa12d>] init_nilfs+0xa21/0xea0 fs/nilfs2/the_nilfs.c:637 [<00000000082e7458>] nilfs_fill_super fs/nilfs2/super.c:1046 [inline] [<00000000082e7458>] nilfs_mount+0x7b4/0xe80 fs/nilfs2/super.c:1316 [<00000000adc3fd88>] legacy_get_tree+0x105/0x210 fs/fs_context.c:592 [<00000000a98c45b8>] vfs_get_tree+0x8e/0x2d0 fs/super.c:1498 [<00000000e96282d3>] do_new_mount fs/namespace.c:2905 [inline] [<00000000e96282d3>] path_mount+0xf9b/0x1990 fs/namespace.c:3235 [<000000003d2eb1b0>] do_mount+0xea/0x100 fs/namespace.c:3248 [<00000000e1ce771a>] __do_sys_mount fs/namespace.c:3456 [inline] [<00000000e1ce771a>] __se_sys_mount fs/namespace.c:3433 [inline] [<00000000e1ce771a>] __x64_sys_mount+0x14b/0x1f0 fs/namespace.c:3433 [<000000007c7f81e8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<000000007c7f81e8>] do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80 [<00000000fd23ff06>] entry_SYSCALL_64_after_hwframe+0x44/0xae If kobject_init_and_add return with error, then the cleanup of kobject is needed because memory may be allocated in kobject_init_and_add without freeing. And the place of cleanup_dev_kobject should use kobject_put to free the memory associated with the kobject. As the section "Kobject removal" of "Documentation/core-api/kobject.rst" says, kobject_del() just makes the kobject "invisible", but it is not cleaned up. And no more cleanup will do after cleanup_dev_kobject, so kobject_put is needed here. Link: https://lkml.kernel.org/r/1625651306-10829-1-git-send-email-konishi.ryusuke@xxxxxxxxx Link: https://lkml.kernel.org/r/1625651306-10829-2-git-send-email-konishi.ryusuke@xxxxxxxxx Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20210629022556.3985106-2-sunnanyong@xxxxxxxxxx Signed-off-by: Nanyong Sun <sunnanyong@xxxxxxxxxx> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/nilfs2/sysfs.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) --- a/fs/nilfs2/sysfs.c~nilfs2-fix-memory-leak-in-nilfs_sysfs_create_device_group +++ a/fs/nilfs2/sysfs.c @@ -986,7 +986,7 @@ int nilfs_sysfs_create_device_group(stru err = kobject_init_and_add(&nilfs->ns_dev_kobj, &nilfs_dev_ktype, NULL, "%s", sb->s_id); if (err) - goto free_dev_subgroups; + goto cleanup_dev_kobject; err = nilfs_sysfs_create_mounted_snapshots_group(nilfs); if (err) @@ -1023,9 +1023,7 @@ delete_mounted_snapshots_group: nilfs_sysfs_delete_mounted_snapshots_group(nilfs); cleanup_dev_kobject: - kobject_del(&nilfs->ns_dev_kobj); - -free_dev_subgroups: + kobject_put(&nilfs->ns_dev_kobj); kfree(nilfs->ns_dev_subgroups); failed_create_device_group: _
