Re: [syzbot] [overlayfs?] memory leak in ovl_parse_param

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
memory leak in ovl_parse_param

BUG: memory leak
unreferenced object 0xffff88814002d0c8 (size 8):
  comm "syz-executor.0", pid 5498, jiffies 4294944229 (age 12.660s)
  hex dump (first 8 bytes):
    2e 00 00 00 00 00 00 00                          ........
  backtrace:
    [<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
    [<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
    [<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
    [<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
    [<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
    [<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
    [<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62
    [<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
    [<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
    [<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
    [<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
    [<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
    [<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
    [<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
    [<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
    [<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
    [<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
    [<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863
    [<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
    [<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
    [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: memory leak
unreferenced object 0xffff8881009ec0c8 (size 8):
  comm "syz-executor.0", pid 5752, jiffies 4294944765 (age 7.300s)
  hex dump (first 8 bytes):
    2e 00 00 00 00 00 00 00                          ........
  backtrace:
    [<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
    [<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
    [<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
    [<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
    [<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
    [<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
    [<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62
    [<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
    [<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
    [<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
    [<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
    [<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
    [<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
    [<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
    [<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
    [<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
    [<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
    [<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863
    [<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
    [<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
    [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: memory leak
unreferenced object 0xffff8881009ec0e0 (size 8):
  comm "syz-executor.0", pid 5754, jiffies 4294944766 (age 7.290s)
  hex dump (first 8 bytes):
    2e 00 00 00 00 00 00 00                          ........
  backtrace:
    [<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
    [<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
    [<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
    [<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
    [<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
    [<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
    [<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62
    [<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
    [<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
    [<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
    [<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
    [<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
    [<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
    [<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
    [<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
    [<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
    [<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
    [<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863
    [<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
    [<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
    [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b



Tested on:

commit:         3f653af2 ovl: fix memory leak in ovl_parse_param()
git tree:       https://github.com/amir73il/linux ovl-fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=13a07ea7680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.