linux-kernel - Re: [PATCH] lib/generic-radix-tree.c: add kmemleak annotations

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Date:   Fri, 4 Oct 2019 15:48:41 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-sctp@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com,
        Kent Overstreet <kent.overstreet@...il.com>,
        Vlad Yasevich <vyasevich@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH] lib/generic-radix-tree.c: add kmemleak annotations

On Thu, Oct 03, 2019 at 11:50:39PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Kmemleak is falsely reporting a leak of the slab allocation in
> sctp_stream_init_ext():
> 
> BUG: memory leak
> unreferenced object 0xffff8881114f5d80 (size 96):
>    comm "syz-executor934", pid 7160, jiffies 4294993058 (age 31.950s)
>    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:
>      [<00000000ce7a1326>] kmemleak_alloc_recursive  include/linux/kmemleak.h:55 [inline]
>      [<00000000ce7a1326>] slab_post_alloc_hook mm/slab.h:439 [inline]
>      [<00000000ce7a1326>] slab_alloc mm/slab.c:3326 [inline]
>      [<00000000ce7a1326>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
>      [<000000007abb7ac9>] kmalloc include/linux/slab.h:547 [inline]
>      [<000000007abb7ac9>] kzalloc include/linux/slab.h:742 [inline]
>      [<000000007abb7ac9>] sctp_stream_init_ext+0x2b/0xa0  net/sctp/stream.c:157
>      [<0000000048ecb9c1>] sctp_sendmsg_to_asoc+0x946/0xa00  net/sctp/socket.c:1882
>      [<000000004483ca2b>] sctp_sendmsg+0x2a8/0x990 net/sctp/socket.c:2102
>      [...]
> 
> But it's freed later.  Kmemleak misses the allocation because its
> pointer is stored in the generic radix tree sctp_stream::out, and the
> generic radix tree uses raw pages which aren't tracked by kmemleak.
> 
> Fix this by adding the kmemleak hooks to the generic radix tree code.
> 
> Reported-by: syzbot+7f3b6b106be8dcdcdeec@...kaller.appspotmail.com
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>