2019-10-09 16:50:13

by Ilya Maximets

[permalink] [raw]
Subject: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
valgrind complain about passing uninitialized stack memory to the
syscall:

Syscall param socketcall.setsockopt() points to uninitialised byte(s)
at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
Uninitialised value was created by a stack allocation
at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)

Padding bytes appeared after introducing of a new 'flags' field.
memset() is required to clear them.

Fixes: 10d30e301732 ("libbpf: add flags to umem config")
Signed-off-by: Ilya Maximets <[email protected]>
---

Version 2:
* Struct initializer replaced with explicit memset(). [Andrii]

tools/lib/bpf/xsk.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index a902838f9fcc..9d5348086203 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
umem->umem_area = umem_area;
xsk_set_umem_config(&umem->config, usr_config);

+ memset(&mr, 0, sizeof(mr));
mr.addr = (uintptr_t)umem_area;
mr.len = size;
mr.chunk_size = umem->config.frame_size;
--
2.17.1


2019-10-09 16:57:59

by Andrii Nakryiko

[permalink] [raw]
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

On Wed, Oct 9, 2019 at 9:49 AM Ilya Maximets <[email protected]> wrote:
>
> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
> valgrind complain about passing uninitialized stack memory to the
> syscall:
>
> Syscall param socketcall.setsockopt() points to uninitialised byte(s)
> at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
> by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
> Uninitialised value was created by a stack allocation
> at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>
> Padding bytes appeared after introducing of a new 'flags' field.
> memset() is required to clear them.
>
> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
> Signed-off-by: Ilya Maximets <[email protected]>
> ---
>

Thanks!

Acked-by: Andrii Nakryiko <[email protected]>

> Version 2:
> * Struct initializer replaced with explicit memset(). [Andrii]
>
> tools/lib/bpf/xsk.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index a902838f9fcc..9d5348086203 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
> umem->umem_area = umem_area;
> xsk_set_umem_config(&umem->config, usr_config);
>
> + memset(&mr, 0, sizeof(mr));
> mr.addr = (uintptr_t)umem_area;
> mr.len = size;
> mr.chunk_size = umem->config.frame_size;
> --
> 2.17.1
>

2019-10-09 22:50:52

by Alexei Starovoitov

[permalink] [raw]
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

On Wed, Oct 9, 2019 at 9:49 AM Ilya Maximets <[email protected]> wrote:
>
> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
> valgrind complain about passing uninitialized stack memory to the
> syscall:
>
> Syscall param socketcall.setsockopt() points to uninitialised byte(s)
> at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
> by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
> Uninitialised value was created by a stack allocation
> at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>
> Padding bytes appeared after introducing of a new 'flags' field.
> memset() is required to clear them.
>
> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
> Signed-off-by: Ilya Maximets <[email protected]>

Applied. Thanks

2019-10-12 23:27:37

by Alexei Starovoitov

[permalink] [raw]
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

On Wed, Oct 09, 2019 at 06:49:29PM +0200, Ilya Maximets wrote:
> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
> valgrind complain about passing uninitialized stack memory to the
> syscall:
>
> Syscall param socketcall.setsockopt() points to uninitialised byte(s)
> at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
> by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
> Uninitialised value was created by a stack allocation
> at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>
> Padding bytes appeared after introducing of a new 'flags' field.
> memset() is required to clear them.
>
> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
> Signed-off-by: Ilya Maximets <[email protected]>
> ---
>
> Version 2:
> * Struct initializer replaced with explicit memset(). [Andrii]
>
> tools/lib/bpf/xsk.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index a902838f9fcc..9d5348086203 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
> umem->umem_area = umem_area;
> xsk_set_umem_config(&umem->config, usr_config);
>
> + memset(&mr, 0, sizeof(mr));
> mr.addr = (uintptr_t)umem_area;
> mr.len = size;
> mr.chunk_size = umem->config.frame_size;

This was already applied. Why did you resend?

2019-10-13 10:21:39

by Ilya Maximets

[permalink] [raw]
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

On 13.10.2019 1:24, Alexei Starovoitov wrote:
> On Wed, Oct 09, 2019 at 06:49:29PM +0200, Ilya Maximets wrote:
>> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
>> valgrind complain about passing uninitialized stack memory to the
>> syscall:
>>
>> Syscall param socketcall.setsockopt() points to uninitialised byte(s)
>> at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
>> by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
>> Uninitialised value was created by a stack allocation
>> at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>>
>> Padding bytes appeared after introducing of a new 'flags' field.
>> memset() is required to clear them.
>>
>> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
>> Signed-off-by: Ilya Maximets <[email protected]>
>> ---
>>
>> Version 2:
>> * Struct initializer replaced with explicit memset(). [Andrii]
>>
>> tools/lib/bpf/xsk.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
>> index a902838f9fcc..9d5348086203 100644
>> --- a/tools/lib/bpf/xsk.c
>> +++ b/tools/lib/bpf/xsk.c
>> @@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>> umem->umem_area = umem_area;
>> xsk_set_umem_config(&umem->config, usr_config);
>>
>> + memset(&mr, 0, sizeof(mr));
>> mr.addr = (uintptr_t)umem_area;
>> mr.len = size;
>> mr.chunk_size = umem->config.frame_size;
>
> This was already applied. Why did you resend?
>

Sorry, it wasn't me. Looking at the mail delivery chain:

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There is some strange server listssympa-test.colorado.edu.
Looks like someone in colorado.edu is testing stuff on production server.

The simplified delivery chain looks like this:

Me -> relay6-d.mail.gandi.net -> vger.kernel.org -> mx.colorado.edu ->
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Best regards, Ilya Maximets.