[PATCH v1 net 0/4] af_unix: Fix four data-races.

[PATCH v1 net 0/4] af_unix: Fix four data-races.

[Kuniyuki Iwashima]

While running syzkaller, KCSAN reported 3 data-races with
systemd-coredump using AF_UNIX sockets.

This series fixes the three and another one inspiered by
one of the reports.


Kuniyuki Iwashima (4):
  af_unix: Fix data-races around user->unix_inflight.
  af_unix: Fix data-race around unix_tot_inflight.
  af_unix: Fix data-races around sk->sk_shutdown.
  af_unix: Fix data race around sk->sk_err.

 net/core/sock.c    | 6 +++---
 net/unix/af_unix.c | 2 +-
 net/unix/scm.c     | 6 +++---
 3 files changed, 7 insertions(+), 7 deletions(-)

-- 
2.30.2

[PATCH v1 net 1/4] af_unix: Fix data-races around user->unix_inflight.

[Kuniyuki Iwashima]

user->unix_inflight is changed under spin_lock(unix_gc_lock),
but too_many_unix_fds() reads it locklessly.

Let's annotate the write/read accesses to user->unix_inflight.

BUG: KCSAN: data-race in unix_attach_fds / unix_inflight

write to 0xffffffff8546f2d0 of 8 bytes by task 44798 on cpu 1:
 unix_inflight+0x157/0x180 net/unix/scm.c:66
 unix_attach_fds+0x147/0x1e0 net/unix/scm.c:123
 unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
 unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
 unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
 unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg+0x148/0x160 net/socket.c:748
 ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
 ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
 __sys_sendmsg+0x94/0x140 net/socket.c:2577
 __do_sys_sendmsg net/socket.c:2586 [inline]
 __se_sys_sendmsg net/socket.c:2584 [inline]
 __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

read to 0xffffffff8546f2d0 of 8 bytes by task 44814 on cpu 0:
 too_many_unix_fds net/unix/scm.c:101 [inline]
 unix_attach_fds+0x54/0x1e0 net/unix/scm.c:110
 unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
 unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
 unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
 unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg+0x148/0x160 net/socket.c:748
 ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
 ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
 __sys_sendmsg+0x94/0x140 net/socket.c:2577
 __do_sys_sendmsg net/socket.c:2586 [inline]
 __se_sys_sendmsg net/socket.c:2584 [inline]
 __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

value changed: 0x000000000000000c -> 0x000000000000000d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 44814 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 712f4aad406b ("unix: properly account for FDs passed over unix sockets")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
Cc: Willy Tarreau <w@1wt.eu>
---
 net/unix/scm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/unix/scm.c b/net/unix/scm.c
index e9dde7176c8a..6ff628f2349f 100644
--- a/net/unix/scm.c
+++ b/net/unix/scm.c
@@ -64,7 +64,7 @@ void unix_inflight(struct user_struct *user, struct file *fp)
 		/* Paired with READ_ONCE() in wait_for_unix_gc() */
 		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
 	}
-	user->unix_inflight++;
+	WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
 	spin_unlock(&unix_gc_lock);
 }
 
@@ -85,7 +85,7 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
 		/* Paired with READ_ONCE() in wait_for_unix_gc() */
 		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
 	}
-	user->unix_inflight--;
+	WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
 	spin_unlock(&unix_gc_lock);
 }
 
@@ -99,7 +99,7 @@ static inline bool too_many_unix_fds(struct task_struct *p)
 {
 	struct user_struct *user = current_user();
 
-	if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
+	if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
 		return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 	return false;
 }
-- 
2.30.2

Re: [PATCH v1 net 1/4] af_unix: Fix data-races around user->unix_inflight.

[Willy Tarreau]

Hi,

On Fri, Sep 01, 2023 at 05:27:05PM -0700, Kuniyuki Iwashima wrote:
> user->unix_inflight is changed under spin_lock(unix_gc_lock),
> but too_many_unix_fds() reads it locklessly.
> 
> Let's annotate the write/read accesses to user->unix_inflight.
> 
> BUG: KCSAN: data-race in unix_attach_fds / unix_inflight
> 
> write to 0xffffffff8546f2d0 of 8 bytes by task 44798 on cpu 1:
>  unix_inflight+0x157/0x180 net/unix/scm.c:66
>  unix_attach_fds+0x147/0x1e0 net/unix/scm.c:123
>  unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
>  unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
>  unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
>  unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
>  sock_sendmsg_nosec net/socket.c:725 [inline]
>  sock_sendmsg+0x148/0x160 net/socket.c:748
>  ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
>  ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
>  __sys_sendmsg+0x94/0x140 net/socket.c:2577
>  __do_sys_sendmsg net/socket.c:2586 [inline]
>  __se_sys_sendmsg net/socket.c:2584 [inline]
>  __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> 
> read to 0xffffffff8546f2d0 of 8 bytes by task 44814 on cpu 0:
>  too_many_unix_fds net/unix/scm.c:101 [inline]
>  unix_attach_fds+0x54/0x1e0 net/unix/scm.c:110
>  unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
>  unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
>  unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
>  unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
>  sock_sendmsg_nosec net/socket.c:725 [inline]
>  sock_sendmsg+0x148/0x160 net/socket.c:748
>  ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
>  ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
>  __sys_sendmsg+0x94/0x140 net/socket.c:2577
>  __do_sys_sendmsg net/socket.c:2586 [inline]
>  __se_sys_sendmsg net/socket.c:2584 [inline]
>  __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> 
> value changed: 0x000000000000000c -> 0x000000000000000d
> 
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 0 PID: 44814 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> 
> Fixes: 712f4aad406b ("unix: properly account for FDs passed over unix sockets")
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---
> Cc: Willy Tarreau <w@1wt.eu>
> ---
>  net/unix/scm.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/unix/scm.c b/net/unix/scm.c
> index e9dde7176c8a..6ff628f2349f 100644
> --- a/net/unix/scm.c
> +++ b/net/unix/scm.c
> @@ -64,7 +64,7 @@ void unix_inflight(struct user_struct *user, struct file *fp)
>  		/* Paired with READ_ONCE() in wait_for_unix_gc() */
>  		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
>  	}
> -	user->unix_inflight++;
> +	WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
>  	spin_unlock(&unix_gc_lock);
>  }
>  
> @@ -85,7 +85,7 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
>  		/* Paired with READ_ONCE() in wait_for_unix_gc() */
>  		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
>  	}
> -	user->unix_inflight--;
> +	WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
>  	spin_unlock(&unix_gc_lock);
>  }
>  
> @@ -99,7 +99,7 @@ static inline bool too_many_unix_fds(struct task_struct *p)
>  {
>  	struct user_struct *user = current_user();
>  
> -	if (unlikely(user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)))
> +	if (unlikely(READ_ONCE(user->unix_inflight) > task_rlimit(p, RLIMIT_NOFILE)))
>  		return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
>  	return false;
>  }

Looks good to me, thanks!
Acked-by: Willy Tarreau <w@1wt.eu>

Willy

Re: [PATCH v1 net 1/4] af_unix: Fix data-races around user->unix_inflight.

[Eric Dumazet]

On Sat, Sep 2, 2023 at 2:28 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> user->unix_inflight is changed under spin_lock(unix_gc_lock),
> but too_many_unix_fds() reads it locklessly.
>
> Let's annotate the write/read accesses to user->unix_inflight.
>
> BUG: KCSAN: data-race in unix_attach_fds / unix_inflight
>
> write to 0xffffffff8546f2d0 of 8 bytes by task 44798 on cpu 1:
>  unix_inflight+0x157/0x180 net/unix/scm.c:66
>  unix_attach_fds+0x147/0x1e0 net/unix/scm.c:123
>  unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
>  unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
>  unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
>  unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
>  sock_sendmsg_nosec net/socket.c:725 [inline]
>  sock_sendmsg+0x148/0x160 net/socket.c:748
>  ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
>  ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
>  __sys_sendmsg+0x94/0x140 net/socket.c:2577
>  __do_sys_sendmsg net/socket.c:2586 [inline]
>  __se_sys_sendmsg net/socket.c:2584 [inline]
>  __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>
> read to 0xffffffff8546f2d0 of 8 bytes by task 44814 on cpu 0:
>  too_many_unix_fds net/unix/scm.c:101 [inline]
>  unix_attach_fds+0x54/0x1e0 net/unix/scm.c:110
>  unix_scm_to_skb net/unix/af_unix.c:1827 [inline]
>  unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1950
>  unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
>  unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
>  sock_sendmsg_nosec net/socket.c:725 [inline]
>  sock_sendmsg+0x148/0x160 net/socket.c:748
>  ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
>  ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
>  __sys_sendmsg+0x94/0x140 net/socket.c:2577
>  __do_sys_sendmsg net/socket.c:2586 [inline]
>  __se_sys_sendmsg net/socket.c:2584 [inline]
>  __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>
> value changed: 0x000000000000000c -> 0x000000000000000d
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 0 PID: 44814 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>
> Fixes: 712f4aad406b ("unix: properly account for FDs passed over unix sockets")
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>

[PATCH v1 net 2/4] af_unix: Fix data-race around unix_tot_inflight.

[Kuniyuki Iwashima]

unix_tot_inflight is changed under spin_lock(unix_gc_lock), but
unix_release_sock() reads it locklessly.

Let's use READ_ONCE() for unix_tot_inflight.

Note that the writer side was marked by commit 9d6d7f1cb67c ("af_unix:
annote lockless accesses to unix_tot_inflight & gc_in_progress")

BUG: KCSAN: data-race in unix_inflight / unix_release_sock

write (marked) to 0xffffffff871852b8 of 4 bytes by task 123 on cpu 1:
 unix_inflight+0x130/0x180 net/unix/scm.c:64
 unix_attach_fds+0x137/0x1b0 net/unix/scm.c:123
 unix_scm_to_skb net/unix/af_unix.c:1832 [inline]
 unix_dgram_sendmsg+0x46a/0x14f0 net/unix/af_unix.c:1955
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg+0x148/0x160 net/socket.c:747
 ____sys_sendmsg+0x4e4/0x610 net/socket.c:2493
 ___sys_sendmsg+0xc6/0x140 net/socket.c:2547
 __sys_sendmsg+0x94/0x140 net/socket.c:2576
 __do_sys_sendmsg net/socket.c:2585 [inline]
 __se_sys_sendmsg net/socket.c:2583 [inline]
 __x64_sys_sendmsg+0x45/0x50 net/socket.c:2583
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

read to 0xffffffff871852b8 of 4 bytes by task 4891 on cpu 0:
 unix_release_sock+0x608/0x910 net/unix/af_unix.c:671
 unix_release+0x59/0x80 net/unix/af_unix.c:1058
 __sock_release+0x7d/0x170 net/socket.c:653
 sock_close+0x19/0x30 net/socket.c:1385
 __fput+0x179/0x5e0 fs/file_table.c:321
 ____fput+0x15/0x20 fs/file_table.c:349
 task_work_run+0x116/0x1a0 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x174/0x180 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:297
 do_syscall_64+0x4b/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4891 Comm: systemd-coredum Not tainted 6.4.0-rc5-01219-gfa0e21fa4443 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 9305cfa4443d ("[AF_UNIX]: Make unix_tot_inflight counter non-atomic")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
Cc: Pavel Emelyanov <xemul@openvz.org>
---
 net/unix/af_unix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 86930a8ed012..3e8a04a13668 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -680,7 +680,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 	 *	  What the above comment does talk about? --ANK(980817)
 	 */
 
-	if (unix_tot_inflight)
+	if (READ_ONCE(unix_tot_inflight))
 		unix_gc();		/* Garbage collect fds */
 }
 
-- 
2.30.2

Re: [PATCH v1 net 2/4] af_unix: Fix data-race around unix_tot_inflight.

[Eric Dumazet]

On Sat, Sep 2, 2023 at 2:28 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> unix_tot_inflight is changed under spin_lock(unix_gc_lock), but
> unix_release_sock() reads it locklessly.
>
> Let's use READ_ONCE() for unix_tot_inflight.
>
> Note that the writer side was marked by commit 9d6d7f1cb67c ("af_unix:
> annote lockless accesses to unix_tot_inflight & gc_in_progress")
>
>
> Fixes: 9305cfa4443d ("[AF_UNIX]: Make unix_tot_inflight counter non-atomic")
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>

[PATCH v1 net 3/4] af_unix: Fix data-races around sk->sk_shutdown.

[Kuniyuki Iwashima]

sk->sk_shutdown is changed under unix_state_lock(sk), but
unix_dgram_sendmsg() calls two functions to read sk_shutdown locklessly.

  sock_alloc_send_pskb
  `- sock_wait_for_wmem

Let's use READ_ONCE() there.

Note that the writer side was marked by commit e1d09c2c2f57 ("af_unix:
Fix data races around sk->sk_shutdown.").

BUG: KCSAN: data-race in sock_alloc_send_pskb / unix_release_sock

write (marked) to 0xffff8880069af12c of 1 bytes by task 1 on cpu 1:
 unix_release_sock+0x75c/0x910 net/unix/af_unix.c:631
 unix_release+0x59/0x80 net/unix/af_unix.c:1053
 __sock_release+0x7d/0x170 net/socket.c:654
 sock_close+0x19/0x30 net/socket.c:1386
 __fput+0x2a3/0x680 fs/file_table.c:384
 ____fput+0x15/0x20 fs/file_table.c:412
 task_work_run+0x116/0x1a0 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x174/0x180 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:297
 do_syscall_64+0x4b/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

read to 0xffff8880069af12c of 1 bytes by task 28650 on cpu 0:
 sock_alloc_send_pskb+0xd2/0x620 net/core/sock.c:2767
 unix_dgram_sendmsg+0x2f8/0x14f0 net/unix/af_unix.c:1944
 unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
 unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg+0x148/0x160 net/socket.c:748
 ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
 ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
 __sys_sendmsg+0x94/0x140 net/socket.c:2577
 __do_sys_sendmsg net/socket.c:2586 [inline]
 __se_sys_sendmsg net/socket.c:2584 [inline]
 __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

value changed: 0x00 -> 0x03

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28650 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/core/sock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index d3c7b53368d2..e3da7eae9338 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2747,7 +2747,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 		if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
 			break;
-		if (sk->sk_shutdown & SEND_SHUTDOWN)
+		if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
 			break;
 		if (sk->sk_err)
 			break;
@@ -2777,7 +2777,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
 			goto failure;
 
 		err = -EPIPE;
-		if (sk->sk_shutdown & SEND_SHUTDOWN)
+		if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
 			goto failure;
 
 		if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))
-- 
2.30.2

Re: [PATCH v1 net 3/4] af_unix: Fix data-races around sk->sk_shutdown.

[Eric Dumazet]

On Sat, Sep 2, 2023 at 2:28 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> sk->sk_shutdown is changed under unix_state_lock(sk), but
> unix_dgram_sendmsg() calls two functions to read sk_shutdown locklessly.
>
>   sock_alloc_send_pskb
>   `- sock_wait_for_wmem
>
> Let's use READ_ONCE() there.
>
> Note that the writer side was marked by commit e1d09c2c2f57 ("af_unix:
> Fix data races around sk->sk_shutdown.").
>
> BUG: KCSAN: data-race in sock_alloc_send_pskb / unix_release_sock
>
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>

[PATCH v1 net 4/4] af_unix: Fix data race around sk->sk_err.

[Kuniyuki Iwashima]

As with sk->sk_shutdown shown in the previous patch, sk->sk_err can be
read locklessly by unix_dgram_sendmsg().

Let's use READ_ONCE() for sk_err as well.

Note that the writer side is marked by commit cc04410af7de ("af_unix:
annotate lockless accesses to sk->sk_err").

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/core/sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index e3da7eae9338..16584e2dd648 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2749,7 +2749,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
 			break;
 		if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
 			break;
-		if (sk->sk_err)
+		if (READ_ONCE(sk->sk_err))
 			break;
 		timeo = schedule_timeout(timeo);
 	}
-- 
2.30.2

Re: [PATCH v1 net 4/4] af_unix: Fix data race around sk->sk_err.

[Eric Dumazet]

On Sat, Sep 2, 2023 at 2:29 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> As with sk->sk_shutdown shown in the previous patch, sk->sk_err can be
> read locklessly by unix_dgram_sendmsg().
>
> Let's use READ_ONCE() for sk_err as well.
>
> Note that the writer side is marked by commit cc04410af7de ("af_unix:
> annotate lockless accesses to sk->sk_err").
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> ---

Title is slightly off, since this is a generic net: change, but this
is fine really ;)

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks.

Re: [PATCH v1 net 0/4] af_unix: Fix four data-races.

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by David S. Miller <davem@davemloft.net>:

On Fri, 1 Sep 2023 17:27:04 -0700 you wrote:
> While running syzkaller, KCSAN reported 3 data-races with
> systemd-coredump using AF_UNIX sockets.
> 
> This series fixes the three and another one inspiered by
> one of the reports.
> 
> 
> [...]

Here is the summary with links:
  - [v1,net,1/4] af_unix: Fix data-races around user->unix_inflight.
    https://git.kernel.org/netdev/net/c/0bc36c0650b2
  - [v1,net,2/4] af_unix: Fix data-race around unix_tot_inflight.
    https://git.kernel.org/netdev/net/c/ade32bd8a738
  - [v1,net,3/4] af_unix: Fix data-races around sk->sk_shutdown.
    https://git.kernel.org/netdev/net/c/afe8764f7634
  - [v1,net,4/4] af_unix: Fix data race around sk->sk_err.
    https://git.kernel.org/netdev/net/c/b192812905e4

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html