Re: [syzbot] memory leak in cap_inode_getsecurity

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    6a010258447d Merge tag 'for-linus' of git://git.armlinux.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15883fee080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2a1dcc1942e30704
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1568846a080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f5e536080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+942d5390db2d9624ced8@xxxxxxxxxxxxxxxxxxxxxxxxx

executing program
BUG: memory leak
unreferenced object 0xffff88810f0ac060 (size 32):
  comm "syz-executor240", pid 3622, jiffies 4294961303 (age 14.040s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff814c6ecd>] __do_krealloc mm/slab_common.c:1185 [inline]
    [<ffffffff814c6ecd>] krealloc+0x4d/0xb0 mm/slab_common.c:1218
    [<ffffffff8162625c>] vfs_getxattr_alloc+0x13c/0x1c0 fs/xattr.c:379
    [<ffffffff822374b2>] cap_inode_getsecurity+0xb2/0x500 security/commoncap.c:400
    [<ffffffff8223d88c>] security_inode_getsecurity+0x7c/0xb0 security/security.c:1441
    [<ffffffff81625a0a>] xattr_getsecurity fs/xattr.c:327 [inline]
    [<ffffffff81625a0a>] vfs_getxattr+0x22a/0x290 fs/xattr.c:423
    [<ffffffff81c0ab02>] ovl_xattr_get+0x62/0xa0 fs/overlayfs/inode.c:404
    [<ffffffff81624742>] __vfs_getxattr+0x72/0xa0 fs/xattr.c:401
    [<ffffffff82236f52>] cap_inode_need_killpriv+0x22/0x40 security/commoncap.c:301
    [<ffffffff8223d773>] security_inode_need_killpriv+0x23/0x60 security/security.c:1419
    [<ffffffff8161074e>] dentry_needs_remove_privs fs/inode.c:1992 [inline]
    [<ffffffff8161074e>] dentry_needs_remove_privs+0x4e/0xa0 fs/inode.c:1982
    [<ffffffff815cfead>] do_truncate+0x7d/0x130 fs/open.c:57
    [<ffffffff815d0169>] vfs_truncate+0x209/0x240 fs/open.c:111
    [<ffffffff815d0268>] do_sys_truncate.part.0+0xc8/0xe0 fs/open.c:134
    [<ffffffff815d0303>] do_sys_truncate fs/open.c:128 [inline]
    [<ffffffff815d0303>] __do_sys_truncate fs/open.c:146 [inline]
    [<ffffffff815d0303>] __se_sys_truncate fs/open.c:144 [inline]
    [<ffffffff815d0303>] __x64_sys_truncate+0x33/0x50 fs/open.c:144
    [<ffffffff845b1955>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff845b1955>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd