[PATCH net 0/3] net: start to replace copy_from_sockptr()

[PATCH net 0/3] net: start to replace copy_from_sockptr()

[Eric Dumazet]

We got several syzbot reports about unsafe copy_from_sockptr()
calls. After fixing some of them, it appears that we could
use a new helper to factorize all the checks in one place.

This series targets net tree, we can later start converting
many call sites in net-next.

Eric Dumazet (3):
  net: add copy_safe_from_sockptr() helper
  mISDN: fix MISDN_TIME_STAMP handling
  nfc: llcp: fix nfc_llcp_setsockopt() unsafe copies

 drivers/isdn/mISDN/socket.c | 10 +++++-----
 include/linux/sockptr.h     | 25 +++++++++++++++++++++++++
 net/nfc/llcp_sock.c         | 12 ++++++------
 3 files changed, 36 insertions(+), 11 deletions(-)

-- 
2.44.0.478.gd926399ef9-goog

[PATCH net 1/3] net: add copy_safe_from_sockptr() helper

[Eric Dumazet]

copy_from_sockptr() helper is unsafe, unless callers
did the prior check against user provided optlen.

Too many callers get this wrong, lets add a helper to
fix them and avoid future copy/paste bugs.

Instead of :

   if (optlen < sizeof(opt)) {
       err = -EINVAL;
       break;
   }
   if (copy_from_sockptr(&opt, optval, sizeof(opt)) {
       err = -EFAULT;
       break;
   }

Use :

   err = copy_safe_from_sockptr(&opt, sizeof(opt),
                                optval, optlen);
   if (err)
       break;

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/sockptr.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
index 307961b41541a620023ad40d3178d47b94768126..b272d6866c87d837e340ce9e78e8fb3423efbddf 100644
--- a/include/linux/sockptr.h
+++ b/include/linux/sockptr.h
@@ -50,11 +50,36 @@ static inline int copy_from_sockptr_offset(void *dst, sockptr_t src,
 	return 0;
 }
 
+/* Deprecated.
+ * This is unsafe, unless caller checked user provided optlen.
+ * Prefer copy_safe_from_sockptr() instead.
+ */
 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
 {
 	return copy_from_sockptr_offset(dst, src, 0, size);
 }
 
+/**
+ * copy_safe_from_sockptr: copy a struct from sockptr
+ * @dst:   Destination address, in kernel space. This buffer must be @ksize
+ *         bytes long.
+ * @ksize: Size of @dst struct.
+ * @optval: Source address. (in user or kernel space)
+ * @optlen: Size of @optval data.
+ *
+ * Returns
+ *  * -EINVAL: @optlen < @ksize
+ *  * -EFAULT: access to userspace failed.
+ *  * 0 : @ksize bytes were copied
+ */
+static inline int copy_safe_from_sockptr(void *dst, size_t ksize,
+					 sockptr_t optval, unsigned int optlen)
+{
+	if (optlen < ksize)
+		return -EINVAL;
+	return copy_from_sockptr(dst, optval, ksize);
+}
+
 static inline int copy_struct_from_sockptr(void *dst, size_t ksize,
 		sockptr_t src, size_t usize)
 {
-- 
2.44.0.478.gd926399ef9-goog

Re: [PATCH net 1/3] net: add copy_safe_from_sockptr() helper

[Jakub Kicinski]

On Mon,  8 Apr 2024 08:28:43 +0000 Eric Dumazet wrote:
> + * Returns
> + *  * -EINVAL: @optlen < @ksize
> + *  * -EFAULT: access to userspace failed.
> + *  * 0 : @ksize bytes were copied

We enabled the "kdoc returns" validation, because people were nit
picking on the list. Apparently there needs to be a colon at the end:

          here
          v
 * Returns:
 *  * -EINVAL: @optlen < @ksize

Fixed when applying.

[PATCH net 2/3] mISDN: fix MISDN_TIME_STAMP handling

[Eric Dumazet]

syzbot reports one unsafe call to copy_from_sockptr() [1]

Use copy_safe_from_sockptr() instead.

[1]

 BUG: KASAN: slab-out-of-bounds in copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
 BUG: KASAN: slab-out-of-bounds in copy_from_sockptr include/linux/sockptr.h:55 [inline]
 BUG: KASAN: slab-out-of-bounds in data_sock_setsockopt+0x46c/0x4cc drivers/isdn/mISDN/socket.c:417
Read of size 4 at addr ffff0000c6d54083 by task syz-executor406/6167

CPU: 1 PID: 6167 Comm: syz-executor406 Not tainted 6.8.0-rc7-syzkaller-g707081b61156 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call trace:
  dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:291
  show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:298
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
  print_address_description mm/kasan/report.c:377 [inline]
  print_report+0x178/0x518 mm/kasan/report.c:488
  kasan_report+0xd8/0x138 mm/kasan/report.c:601
  __asan_report_load_n_noabort+0x1c/0x28 mm/kasan/report_generic.c:391
  copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
  copy_from_sockptr include/linux/sockptr.h:55 [inline]
  data_sock_setsockopt+0x46c/0x4cc drivers/isdn/mISDN/socket.c:417
  do_sock_setsockopt+0x2a0/0x4e0 net/socket.c:2311
  __sys_setsockopt+0x128/0x1a8 net/socket.c:2334
  __do_sys_setsockopt net/socket.c:2343 [inline]
  __se_sys_setsockopt net/socket.c:2340 [inline]
  __arm64_sys_setsockopt+0xb8/0xd4 net/socket.c:2340
  __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:133
  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:152
  el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

Fixes: 1b2b03f8e514 ("Add mISDN core files")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Karsten Keil <isdn@linux-pingi.de>
---
 drivers/isdn/mISDN/socket.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/isdn/mISDN/socket.c b/drivers/isdn/mISDN/socket.c
index 2776ca5fc33f39019062b3d9fb8f02547a5e4139..b215b28cad7b76a5764bda8021cece74ec5cd40f 100644
--- a/drivers/isdn/mISDN/socket.c
+++ b/drivers/isdn/mISDN/socket.c
@@ -401,23 +401,23 @@ data_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 }
 
 static int data_sock_setsockopt(struct socket *sock, int level, int optname,
-				sockptr_t optval, unsigned int len)
+				sockptr_t optval, unsigned int optlen)
 {
 	struct sock *sk = sock->sk;
 	int err = 0, opt = 0;
 
 	if (*debug & DEBUG_SOCKET)
 		printk(KERN_DEBUG "%s(%p, %d, %x, optval, %d)\n", __func__, sock,
-		       level, optname, len);
+		       level, optname, optlen);
 
 	lock_sock(sk);
 
 	switch (optname) {
 	case MISDN_TIME_STAMP:
-		if (copy_from_sockptr(&opt, optval, sizeof(int))) {
-			err = -EFAULT;
+		err = copy_safe_from_sockptr(&opt, sizeof(opt),
+					     optval, optlen);
+		if (err)
 			break;
-		}
 
 		if (opt)
 			_pms(sk)->cmask |= MISDN_TIME_STAMP;
-- 
2.44.0.478.gd926399ef9-goog

[PATCH net 3/3] nfc: llcp: fix nfc_llcp_setsockopt() unsafe copies

[Eric Dumazet]

syzbot reported unsafe calls to copy_from_sockptr() [1]

Use copy_safe_from_sockptr() instead.

[1]

BUG: KASAN: slab-out-of-bounds in copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
 BUG: KASAN: slab-out-of-bounds in copy_from_sockptr include/linux/sockptr.h:55 [inline]
 BUG: KASAN: slab-out-of-bounds in nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
Read of size 4 at addr ffff88801caa1ec3 by task syz-executor459/5078

CPU: 0 PID: 5078 Comm: syz-executor459 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
  print_address_description mm/kasan/report.c:377 [inline]
  print_report+0x169/0x550 mm/kasan/report.c:488
  kasan_report+0x143/0x180 mm/kasan/report.c:601
  copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
  copy_from_sockptr include/linux/sockptr.h:55 [inline]
  nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
  do_sock_setsockopt+0x3b1/0x720 net/socket.c:2311
  __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
  __do_sys_setsockopt net/socket.c:2343 [inline]
  __se_sys_setsockopt net/socket.c:2340 [inline]
  __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
 do_syscall_64+0xfd/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f7fac07fd89
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 00 00 90 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 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff660eb788 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f7fac07fd89
RDX: 0000000000000000 RSI: 0000000000000118 RDI: 0000000000000004
RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000020000a80 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
 net/nfc/llcp_sock.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c
index 819157bbb5a2c6ef775633931721490b747f2fc8..d5344563e525c9bc436d5ad0b84380f0bcae62a8 100644
--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -252,10 +252,10 @@ static int nfc_llcp_setsockopt(struct socket *sock, int level, int optname,
 			break;
 		}
 
-		if (copy_from_sockptr(&opt, optval, sizeof(u32))) {
-			err = -EFAULT;
+		err = copy_safe_from_sockptr(&opt, sizeof(opt),
+					     optval, optlen);
+		if (err)
 			break;
-		}
 
 		if (opt > LLCP_MAX_RW) {
 			err = -EINVAL;
@@ -274,10 +274,10 @@ static int nfc_llcp_setsockopt(struct socket *sock, int level, int optname,
 			break;
 		}
 
-		if (copy_from_sockptr(&opt, optval, sizeof(u32))) {
-			err = -EFAULT;
+		err = copy_safe_from_sockptr(&opt, sizeof(opt),
+					     optval, optlen);
+		if (err)
 			break;
-		}
 
 		if (opt > LLCP_MAX_MIUX) {
 			err = -EINVAL;
-- 
2.44.0.478.gd926399ef9-goog

Re: [PATCH net 3/3] nfc: llcp: fix nfc_llcp_setsockopt() unsafe copies

[Krzysztof Kozlowski]

On 08/04/2024 10:28, Eric Dumazet wrote:
> syzbot reported unsafe calls to copy_from_sockptr() [1]
> 
> Use copy_safe_from_sockptr() instead.
> 
> [1]
> 
> BUG: KASAN: slab-out-of-bounds in copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
>  BUG: KASAN: slab-out-of-bounds in copy_from_sockptr include/linux/sockptr.h:55 [inline]
>  BUG: KASAN: slab-out-of-bounds in nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
> Read of size 4 at addr ffff88801caa1ec3 by task syz-executor459/5078
> 
> CPU: 0 PID: 5078 Comm: syz-executor459 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> Call Trace:
>  <TASK>
>   __dump_stack lib/dump_stack.c:88 [inline]
>   dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
>   print_address_description mm/kasan/report.c:377 [inline]
>   print_report+0x169/0x550 mm/kasan/report.c:488
>   kasan_report+0x143/0x180 mm/kasan/report.c:601
>   copy_from_sockptr_offset include/linux/sockptr.h:49 [inline]
>   copy_from_sockptr include/linux/sockptr.h:55 [inline]
>   nfc_llcp_setsockopt+0x6c2/0x850 net/nfc/llcp_sock.c:255
>   do_sock_setsockopt+0x3b1/0x720 net/socket.c:2311
>   __sys_setsockopt+0x1ae/0x250 net/socket.c:2334
>   __do_sys_setsockopt net/socket.c:2343 [inline]
>   __se_sys_setsockopt net/socket.c:2340 [inline]
>   __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2340
>  do_syscall_64+0xfd/0x240
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
> RIP: 0033:0x7f7fac07fd89
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 91 18 00 00 90 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 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff660eb788 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f7fac07fd89
> RDX: 0000000000000000 RSI: 0000000000000118 RDI: 0000000000000004
> RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
> R10: 0000000020000a80 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

I received only this patch, so I don't know what
copy_safe_from_sockptr() is doing, but I guess it respects amount of
data in optval, so looks reasonable.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof

Re: [PATCH net 0/3] net: start to replace copy_from_sockptr()

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon,  8 Apr 2024 08:28:42 +0000 you wrote:
> We got several syzbot reports about unsafe copy_from_sockptr()
> calls. After fixing some of them, it appears that we could
> use a new helper to factorize all the checks in one place.
> 
> This series targets net tree, we can later start converting
> many call sites in net-next.
> 
> [...]

Here is the summary with links:
  - [net,1/3] net: add copy_safe_from_sockptr() helper
    https://git.kernel.org/netdev/net/c/6309863b31dd
  - [net,2/3] mISDN: fix MISDN_TIME_STAMP handling
    https://git.kernel.org/netdev/net/c/138b787804f4
  - [net,3/3] nfc: llcp: fix nfc_llcp_setsockopt() unsafe copies
    https://git.kernel.org/netdev/net/c/7a87441c9651

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

RE: [PATCH net 0/3] net: start to replace copy_from_sockptr()

[David Laight]

From: Eric Dumazet
> Sent: 08 April 2024 09:29
> 
> We got several syzbot reports about unsafe copy_from_sockptr()
> calls. After fixing some of them, it appears that we could
> use a new helper to factorize all the checks in one place.
> 
> This series targets net tree, we can later start converting
> many call sites in net-next.

I have wondered if 'sockptr' should be changed to include the
length and then passed by reference.
That would work 'readonly' for most code, but there are some strange
options that don't obey the expected rules.
At least one has a 'record count' in the 'normal' buffer and the
rest of the data follows - an accident waiting to happen
(especially if called by bpf).

I must find time to prod the bpf people about changing sockptr_t
to be a struct instead of a union - also safer.

The other obvious change is to pull the usercopy for the length
all the way out of getsockopt() to the syscall wrapper.
I started writing a patch to use the return value for the updated
length - but some of the code is too perverted.

	David

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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)