linux-kernel - Re: [PATCH bpf-next v2] bpf: fix segmentation fault of test

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Message-ID: <066bc6b8-8e08-e473-b454-4544e99ad7e0@iogearbox.net>
Date:   Tue, 11 Aug 2020 15:19:59 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jianlin Lv <Jianlin.Lv@....com>, bpf@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, ast@...nel.org, yhs@...com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v2] bpf: fix segmentation fault of test_progs

On 8/10/20 5:39 PM, Jianlin Lv wrote:
> test_progs reports the segmentation fault as below
> 
> $ sudo ./test_progs -t mmap --verbose
> test_mmap:PASS:skel_open_and_load 0 nsec
> ......
> test_mmap:PASS:adv_mmap1 0 nsec
> test_mmap:PASS:adv_mmap2 0 nsec
> test_mmap:PASS:adv_mmap3 0 nsec
> test_mmap:PASS:adv_mmap4 0 nsec
> Segmentation fault
> 
> This issue was triggered because mmap() and munmap() used inconsistent
> length parameters; mmap() creates a new mapping of 3*page_size, but the
> length parameter set in the subsequent re-map and munmap() functions is
> 4*page_size; this leads to the destruction of the process space.
> 
> To fix this issue, first create 4 pages of anonymous mapping,then do all
> the mmap() with MAP_FIXED.
> 
> Another issue is that when unmap the second page fails, the length
> parameter to delete tmp1 mappings should be 4*page_size.
> 
> Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>

Applied, thanks!