• Steven Rostedt's avatar
    sysctl: suppress kmemleak messages · fd4b616b
    Steven Rostedt authored
    register_sysctl_table() is a strange function, as it makes internal
    allocations (a header) to register a sysctl_table.  This header is a
    handle to the table that is created, and can be used to unregister the
    table.  But if the table is permanent and never unregistered, the header
    acts the same as a static variable.
    
    Unfortunately, this allocation of memory that is never expected to be
    freed fools kmemleak in thinking that we have leaked memory.  For those
    sysctl tables that are never unregistered, and have no pointer referencing
    them, kmemleak will think that these are memory leaks:
    
    unreferenced object 0xffff880079fb9d40 (size 192):
      comm "swapper/0", pid 0, jiffies 4294667316 (age 12614.152s)
      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:
        [<ffffffff8146b590>] kmemleak_alloc+0x73/0x98
        [<ffffffff8110a935>] kmemleak_alloc_recursive.constprop.42+0x16/0x18
        [<ffffffff8110b852>] __kmalloc+0x107/0x153
        [<ffffffff8116fa72>] kzalloc.constprop.8+0xe/0x10
        [<ffffffff811703c9>] __register_sysctl_paths+0xe1/0x160
        [<ffffffff81170463>] register_sysctl_paths+0x1b/0x1d
        [<ffffffff8117047d>] register_sysctl_table+0x18/0x1a
        [<ffffffff81afb0a1>] sysctl_init+0x10/0x14
        [<ffffffff81b05a6f>] proc_sys_init+0x2f/0x31
        [<ffffffff81b0584c>] proc_root_init+0xa5/0xa7
        [<ffffffff81ae5b7e>] start_kernel+0x3d0/0x40a
        [<ffffffff81ae52a7>] x86_64_start_reservations+0xae/0xb2
        [<ffffffff81ae53ad>] x86_64_start_kernel+0x102/0x111
        [<ffffffffffffffff>] 0xffffffffffffffff
    
    The sysctl_base_table used by sysctl itself is one such instance that
    registers the table to never be unregistered.
    
    Use kmemleak_not_leak() to suppress the kmemleak false positive.
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    fd4b616b
sysctl.c 58 KB