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

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_... Syzkaller repro code: https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_... Syzkaller repro syscall steps: https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_... Syzkaller report: https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_... Kconfig(make olddefconfig): https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_... Bisect info: https://github.com/laifryiee/syzkaller_logs/tree/main/241009_103423_do_sock_... bzImage: https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/241009_10342... Issue dmesg: https://github.com/laifryiee/syzkaller_logs/blob/main/241009_103423_do_sock_...

" [ 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@google.com Signed-off-by: Kaiyuan Zhang kaiyuanz@google.com Signed-off-by: Mina Almasry almasrymina@google.com Reviewed-by: Pavel Begunkov asml.silence@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com

---

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@google.com. 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