Re: [PATCH net-next v25 10/13] net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags

From: Lai, Yi
Date: Thu Oct 10 2024 - 07:18:10 EST

Hi Mina Almasry,

Greetings!

I used Syzkaller and found that there is BUG: soft lockup inqt in linux-next tree next-20241008

After bisection and the first bad commit is:
"
678f6e28b5f6 net: add SO_DEVMEM_DONTNEED setsockopt to release RX frags
"

All detailed into can be found at:
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt
Syzkaller repro code:
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt/repro.c
Syzkaller repro syscall steps:
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt/repro.prog
Syzkaller report:
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt/repro.report
Kconfig(make olddefconfig):
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt/kconfig_origin
Bisect info:
https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_setsockopt/bisect_info.log
bzImage:
https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/241009_103423_do_sock_setsockopt/bzImage_8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b
Issue dmesg:
https://github.com/laifryiee/syzkaller_logs/blob/main/241009_103423_do_sock_setsockopt/8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b_dmesg.log

"
[ 48.825073] ? __lock_acquire+0x1b0f/0x5c90
[ 48.825419] ? __pfx___lock_acquire+0x10/0x10
[ 48.825774] sock_setsockopt+0x68/0x90
[ 48.826117] do_sock_setsockopt+0x3fb/0x480
[ 48.826455] ? __pfx_do_sock_setsockopt+0x10/0x10
[ 48.826829] ? lock_release+0x441/0x870
[ 48.827140] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
[ 48.827558] ? fdget+0x188/0x230
[ 48.827846] __sys_setsockopt+0x131/0x200
[ 48.828184] ? __pfx___sys_setsockopt+0x10/0x10
[ 48.828551] ? seqcount_lockdep_reader_access.constprop.0+0xc0/0xd0
[ 48.829042] ? __sanitizer_cov_trace_cmp4+0x1a/0x20
[ 48.829425] ? ktime_get_coarse_real_ts64+0xbf/0xf0
[ 48.829817] __x64_sys_setsockopt+0xc6/0x160
[ 48.830160] ? syscall_trace_enter+0x14a/0x230
[ 48.830520] x64_sys_call+0x6cf/0x20d0
[ 48.830825] do_syscall_64+0x6d/0x140
[ 48.831124] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 48.831517] RIP: 0033:0x7f26cdc3ee5d
[ 48.831804] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 93 af 1b 00 f7 d8 64 89 01 48
[ 48.833180] RSP: 002b:00007fff33f36278 EFLAGS: 00000213 ORIG_RAX: 0000000000000036
[ 48.833756] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26cdc3ee5d
[ 48.834294] RDX: 0000000000000050 RSI: 0000000000000001 RDI: 0000000000000003
[ 48.834830] RBP: 00007fff33f36290 R08: 0000000000000010 R09: 00007fff33f36290
[ 48.835368] R10: 0000000020000080 R11: 0000000000000213 R12: 00007fff33f363e8
[ 48.835906] R13: 000000000040178f R14: 0000000000403e08 R15: 00007f26cde51000
[ 48.836466] </TASK>
[ 48.836648] Kernel panic - not syncing: softlockup: hung tasks
[ 48.837096] CPU: 1 UID: 0 PID: 729 Comm: repro Tainted: G L 6.12.0-rc2-8cf0b93919e1 #1
[ 48.837796] Tainted: [L]=SOFTLOCKUP
[ 48.838071] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 48.838916] Call Trace:
[ 48.839113] <IRQ>
[ 48.839282] dump_stack_lvl+0x42/0x150
[ 48.839584] dump_stack+0x19/0x20
[ 48.839846] panic+0x703/0x790
[ 48.840100] ? __pfx_panic+0x10/0x10
[ 48.840394] ? watchdog_timer_fn+0x599/0x6b0
[ 48.840727] ? watchdog_timer_fn+0x58c/0x6b0
[ 48.841065] watchdog_timer_fn+0x5aa/0x6b0
[ 48.841382] ? __pfx_watchdog_timer_fn+0x10/0x10
[ 48.841743] __hrtimer_run_queues+0x5d6/0xc30
[ 48.842091] ? __pfx___hrtimer_run_queues+0x10/0x10
[ 48.842473] hrtimer_interrupt+0x324/0x7a0
[ 48.842802] __sysvec_apic_timer_interrupt+0x10b/0x410
[ 48.843198] ? debug_smp_processor_id+0x20/0x30
[ 48.843551] sysvec_apic_timer_interrupt+0xaf/0xd0
[ 48.843922] </IRQ>
[ 48.844101] <TASK>
[ 48.844275] asm_sysvec_apic_timer_interrupt+0x1f/0x30
[ 48.844711] RIP: 0010:__sanitizer_cov_trace_pc+0x45/0x70
[ 48.845130] Code: a9 00 01 ff 00 74 1d f6 c4 01 74 43 a9 00 00 0f 00 75 3c a9 00 00 f0 00 75 35 8b 82 04 1e 00 00 85 c0 74 2b 8b 82 e0 1d 00 00 <83> f8 02 75 20 48 8b 8a e8 1d 00 00 8b 92 e4 1d 00 00 48 8b 01 48
[ 48.846480] RSP: 0018:ffff8880239cf790 EFLAGS: 00000246
[ 48.846876] RAX: 0000000000000000 RBX: ffff8880239cf900 RCX: ffffffff8581c19f
[ 48.847407] RDX: ffff88801a818000 RSI: ffffffff8581c1d5 RDI: 0000000000000007
[ 48.847933] RBP: ffff8880239cf790 R08: 0000000000000001 R09: ffffed1004739f23
[ 48.848472] R10: 0000000077cc006e R11: 0000000000000001 R12: 0000000000000000
[ 48.849002] R13: 0000000077cc006e R14: ffff8880239cf918 R15: 0000000000000000
[ 48.849536] ? xas_start+0x11f/0x730
[ 48.849818] ? xas_start+0x155/0x730
[ 48.850101] xas_start+0x155/0x730
[ 48.850372] xas_load+0x2f/0x520
[ 48.850629] ? irqentry_exit+0x3e/0xa0
[ 48.850922] ? sysvec_apic_timer_interrupt+0x6a/0xd0
[ 48.851304] xas_store+0x1165/0x1ad0
[ 48.851588] ? __this_cpu_preempt_check+0x21/0x30
[ 48.851950] ? irqentry_exit+0x3e/0xa0
[ 48.852254] __xa_erase+0xc6/0x180
[ 48.852524] ? __pfx___xa_erase+0x10/0x10
[ 48.852842] ? __xa_erase+0xf1/0x180
[ 48.853123] ? sock_devmem_dontneed+0x42c/0x6d0
[ 48.853480] sock_devmem_dontneed+0x3a8/0x6d0
[ 48.853829] ? __pfx_sock_devmem_dontneed+0x10/0x10
[ 48.854205] ? trace_lock_acquire+0x139/0x1b0
[ 48.854548] ? lock_acquire+0x80/0xb0
[ 48.854833] ? __might_fault+0xf1/0x1b0
[ 48.855133] ? __might_fault+0xf1/0x1b0
[ 48.855437] ? __sanitizer_cov_trace_const_cmp8+0x1c/0x30
[ 48.855849] sk_setsockopt+0x480/0x3c60
[ 48.856158] ? __pfx_sk_setsockopt+0x10/0x10
[ 48.856491] ? __kasan_check_read+0x15/0x20
[ 48.856814] ? __lock_acquire+0x1b0f/0x5c90
[ 48.857144] ? __pfx___lock_acquire+0x10/0x10
[ 48.857488] sock_setsockopt+0x68/0x90
[ 48.857785] do_sock_setsockopt+0x3fb/0x480
[ 48.858110] ? __pfx_do_sock_setsockopt+0x10/0x10
[ 48.858474] ? lock_release+0x441/0x870
[ 48.858776] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
[ 48.859184] ? fdget+0x188/0x230
[ 48.859448] __sys_setsockopt+0x131/0x200
[ 48.859764] ? __pfx___sys_setsockopt+0x10/0x10
[ 48.860123] ? seqcount_lockdep_reader_access.constprop.0+0xc0/0xd0
[ 48.860598] ? __sanitizer_cov_trace_cmp4+0x1a/0x20
[ 48.860982] ? ktime_get_coarse_real_ts64+0xbf/0xf0
[ 48.861370] __x64_sys_setsockopt+0xc6/0x160
[ 48.861710] ? syscall_trace_enter+0x14a/0x230
[ 48.862057] x64_sys_call+0x6cf/0x20d0
[ 48.862350] do_syscall_64+0x6d/0x140
[ 48.862639] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 48.863023] RIP: 0033:0x7f26cdc3ee5d
[ 48.863301] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 93 af 1b 00 f7 d8 64 89 01 48
[ 48.864659] RSP: 002b:00007fff33f36278 EFLAGS: 00000213 ORIG_RAX: 0000000000000036
[ 48.865223] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26cdc3ee5d
"

I hope you find it useful.

Regards,
Yi Lai

---

If you don't need the following environment to reproduce the problem or if you
already have one reproduced environment, please ignore the following information.

How to reproduce:
git clone https://gitlab.com/xupengfe/repro_vm_env.git
cd repro_vm_env
tar -xvf repro_vm_env.tar.gz
cd repro_vm_env; ./start3.sh // it needs qemu-system-x86_64 and I used v7.1.0
// start3.sh will load bzImage_2241ab53cbb5cdb08a6b2d4688feb13971058f65 v6.2-rc5 kernel
// You could change the bzImage_xxx as you want
// Maybe you need to remove line "-drive if=pflash,format=raw,readonly=on,file=./OVMF_CODE.fd \" for different qemu version
You could use below command to log in, there is no password for root.
ssh -p 10023 root@localhost

After login vm(virtual machine) successfully, you could transfer reproduced
binary to the vm by below way, and reproduce the problem in vm:
gcc -pthread -o repro repro.c
scp -P 10023 repro root@localhost:/root/

Get the bzImage for target kernel:
Please use target kconfig and copy it to kernel_src/.config
make olddefconfig
make -jx bzImage //x should equal or less than cpu num your pc has

Fill the bzImage file into above start3.sh to load the target kernel in vm.


Tips:
If you already have qemu-system-x86_64, please ignore below info.
If you want to install qemu v7.1.0 version:
git clone https://github.com/qemu/qemu.git
cd qemu
git checkout -f v7.1.0
mkdir build
cd build
yum install -y ninja-build.x86_64
yum -y install libslirp-devel.x86_64
../configure --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-sdl --enable-usb-redir --enable-slirp
make
make install

On Mon, Sep 09, 2024 at 05:43:15AM +0000, Mina Almasry wrote:
> Add an interface for the user to notify the kernel that it is done
> reading the devmem dmabuf frags returned as cmsg. The kernel will
> drop the reference on the frags to make them available for reuse.
>
> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
> Signed-off-by: Kaiyuan Zhang <kaiyuanz@xxxxxxxxxx>
> Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
> Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
>
> ---
>
> v16:
> - Use sk_is_tcp().
> - Fix unnamed 128 DONTNEED limit (David).
> - Fix kernel allocating for 128 tokens even if the user didn't ask for
> that much (Eric).
> - Fix number assignement (Arnd).
>
> v10:
> - Fix leak of tokens (Nikolay).
>
> v7:
> - Updated SO_DEVMEM_* uapi to use the next available entry (Arnd).
>
> v6:
> - Squash in locking optimizations from edumazet@xxxxxxxxxx. With his
> changes we lock the xarray once per sock_devmem_dontneed operation
> rather than once per frag.
>
> Changes in v1:
> - devmemtoken -> dmabuf_token (David).
> - Use napi_pp_put_page() for refcounting (Yunsheng).
> - Fix build error with missing socket options on other asms.
>
> ---
> arch/alpha/include/uapi/asm/socket.h | 1 +
> arch/mips/include/uapi/asm/socket.h | 1 +
> arch/parisc/include/uapi/asm/socket.h | 1 +
> arch/sparc/include/uapi/asm/socket.h | 1 +
> include/uapi/asm-generic/socket.h | 1 +
> include/uapi/linux/uio.h | 4 ++
> net/core/sock.c | 68 +++++++++++++++++++++++++++
> 7 files changed, 77 insertions(+)
>
> diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> index ef4656a41058..251b73c5481e 100644
> --- a/arch/alpha/include/uapi/asm/socket.h
> +++ b/arch/alpha/include/uapi/asm/socket.h
> @@ -144,6 +144,7 @@
> #define SCM_DEVMEM_LINEAR SO_DEVMEM_LINEAR
> #define SO_DEVMEM_DMABUF 79
> #define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
> +#define SO_DEVMEM_DONTNEED 80
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
> index 414807d55e33..8ab7582291ab 100644
> --- a/arch/mips/include/uapi/asm/socket.h
> +++ b/arch/mips/include/uapi/asm/socket.h
> @@ -155,6 +155,7 @@
> #define SCM_DEVMEM_LINEAR SO_DEVMEM_LINEAR
> #define SO_DEVMEM_DMABUF 79
> #define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
> +#define SO_DEVMEM_DONTNEED 80
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
> index 2b817efd4544..38fc0b188e08 100644
> --- a/arch/parisc/include/uapi/asm/socket.h
> +++ b/arch/parisc/include/uapi/asm/socket.h
> @@ -136,6 +136,7 @@
> #define SCM_DEVMEM_LINEAR SO_DEVMEM_LINEAR
> #define SO_DEVMEM_DMABUF 79
> #define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
> +#define SO_DEVMEM_DONTNEED 80
>
> #if !defined(__KERNEL__)
>
> diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
> index 00248fc68977..57084ed2f3c4 100644
> --- a/arch/sparc/include/uapi/asm/socket.h
> +++ b/arch/sparc/include/uapi/asm/socket.h
> @@ -137,6 +137,7 @@
> #define SCM_DEVMEM_LINEAR SO_DEVMEM_LINEAR
> #define SO_DEVMEM_DMABUF 0x0058
> #define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
> +#define SO_DEVMEM_DONTNEED 0x0059
>
> #if !defined(__KERNEL__)
>
> diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
> index e993edc9c0ee..3b4e3e815602 100644
> --- a/include/uapi/asm-generic/socket.h
> +++ b/include/uapi/asm-generic/socket.h
> @@ -139,6 +139,7 @@
> #define SCM_DEVMEM_LINEAR SO_DEVMEM_LINEAR
> #define SO_DEVMEM_DMABUF 79
> #define SCM_DEVMEM_DMABUF SO_DEVMEM_DMABUF
> +#define SO_DEVMEM_DONTNEED 80
>
> #if !defined(__KERNEL__)
>
> diff --git a/include/uapi/linux/uio.h b/include/uapi/linux/uio.h
> index 3a22ddae376a..d17f8fcd93ec 100644
> --- a/include/uapi/linux/uio.h
> +++ b/include/uapi/linux/uio.h
> @@ -33,6 +33,10 @@ struct dmabuf_cmsg {
> */
> };
>
> +struct dmabuf_token {
> + __u32 token_start;
> + __u32 token_count;
> +};
> /*
> * UIO_MAXIOV shall be at least 16 1003.1g (5.4.1.1)
> */
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 468b1239606c..bbb57b5af0b1 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -124,6 +124,7 @@
> #include <linux/netdevice.h>
> #include <net/protocol.h>
> #include <linux/skbuff.h>
> +#include <linux/skbuff_ref.h>
> #include <net/net_namespace.h>
> #include <net/request_sock.h>
> #include <net/sock.h>
> @@ -1049,6 +1050,69 @@ static int sock_reserve_memory(struct sock *sk, int bytes)
> return 0;
> }
>
> +#ifdef CONFIG_PAGE_POOL
> +
> +/* This is the number of tokens that the user can SO_DEVMEM_DONTNEED in
> + * 1 syscall. The limit exists to limit the amount of memory the kernel
> + * allocates to copy these tokens.
> + */
> +#define MAX_DONTNEED_TOKENS 128
> +
> +static noinline_for_stack int
> +sock_devmem_dontneed(struct sock *sk, sockptr_t optval, unsigned int optlen)
> +{
> + unsigned int num_tokens, i, j, k, netmem_num = 0;
> + struct dmabuf_token *tokens;
> + netmem_ref netmems[16];
> + int ret = 0;
> +
> + if (!sk_is_tcp(sk))
> + return -EBADF;
> +
> + if (optlen % sizeof(struct dmabuf_token) ||
> + optlen > sizeof(*tokens) * MAX_DONTNEED_TOKENS)
> + return -EINVAL;
> +
> + tokens = kvmalloc_array(optlen, sizeof(*tokens), GFP_KERNEL);
> + if (!tokens)
> + return -ENOMEM;
> +
> + num_tokens = optlen / sizeof(struct dmabuf_token);
> + if (copy_from_sockptr(tokens, optval, optlen)) {
> + kvfree(tokens);
> + return -EFAULT;
> + }
> +
> + xa_lock_bh(&sk->sk_user_frags);
> + for (i = 0; i < num_tokens; i++) {
> + for (j = 0; j < tokens[i].token_count; j++) {
> + netmem_ref netmem = (__force netmem_ref)__xa_erase(
> + &sk->sk_user_frags, tokens[i].token_start + j);
> +
> + if (netmem &&
> + !WARN_ON_ONCE(!netmem_is_net_iov(netmem))) {
> + netmems[netmem_num++] = netmem;
> + if (netmem_num == ARRAY_SIZE(netmems)) {
> + xa_unlock_bh(&sk->sk_user_frags);
> + for (k = 0; k < netmem_num; k++)
> + WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
> + netmem_num = 0;
> + xa_lock_bh(&sk->sk_user_frags);
> + }
> + ret++;
> + }
> + }
> + }
> +
> + xa_unlock_bh(&sk->sk_user_frags);
> + for (k = 0; k < netmem_num; k++)
> + WARN_ON_ONCE(!napi_pp_put_page(netmems[k]));
> +
> + kvfree(tokens);
> + return ret;
> +}
> +#endif
> +
> void sockopt_lock_sock(struct sock *sk)
> {
> /* When current->bpf_ctx is set, the setsockopt is called from
> @@ -1211,6 +1275,10 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
> ret = -EOPNOTSUPP;
> return ret;
> }
> +#ifdef CONFIG_PAGE_POOL
> + case SO_DEVMEM_DONTNEED:
> + return sock_devmem_dontneed(sk, optval, optlen);
> +#endif
> }
>
> sockopt_lock_sock(sk);
> --
> 2.46.0.469.g59c65b2a67-goog
>