[syzbot] [tipc?] KMSAN: uninit-value in tipc_rcv (2)

[syzbot] [tipc?] KMSAN: uninit-value in tipc_rcv (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4871b7cb27f4 Merge tag 'v6.16-rc6-smb3-client-fixes' of gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15bbe38c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5227c65742122bdd
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e2e34a7999ba/disk-4871b7cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/834fdc8dbc07/vmlinux-4871b7cb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/617fadfb9a8e/bzImage-4871b7cb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9a4fbb77c9d4aacd3388@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_l2_rcv_msg+0x213/0x320 net/tipc/bearer.c:668
 __netif_receive_skb_list_ptype net/core/dev.c:6025 [inline]
 __netif_receive_skb_list_core+0x133b/0x16b0 net/core/dev.c:6067
 __netif_receive_skb_list net/core/dev.c:6119 [inline]
 netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6210
 gro_normal_list include/net/gro.h:532 [inline]
 napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6580
 napi_complete include/linux/netdevice.h:588 [inline]
 tun_get_user+0x4ac4/0x6b40 drivers/net/tun.c:1909
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 do_iter_readv_writev+0x94a/0xba0 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __ia32_sys_writev+0x9c/0xf0 fs/read_write.c:1168
 ia32_sys_call+0x3f2a/0x42c0 arch/x86/include/generated/asm/syscalls_32.h:147
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4154 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_node_noprof+0x818/0xf00 mm/slub.c:4249
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:812
 napi_get_frags+0xab/0x250 net/core/gro.c:673
 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
 tun_get_user+0x1246/0x6b40 drivers/net/tun.c:1772
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1984
 do_iter_readv_writev+0x94a/0xba0 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __ia32_sys_writev+0x9c/0xf0 fs/read_write.c:1168
 ia32_sys_call+0x3f2a/0x42c0 arch/x86/include/generated/asm/syscalls_32.h:147
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xb0/0x150 arch/x86/entry/syscall_32.c:306
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/syscall_32.c:331
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:369
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

CPU: 0 UID: 0 PID: 15202 Comm: syz.3.3410 Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


---
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Re: [syzbot] [tipc?] KMSAN: uninit-value in tipc_rcv (2)

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    89748acdf226 Merge tag 'drm-next-2025-08-01' of https://gi..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1395bcf0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7ff65239b4835001
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1625ff82580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=131bb834580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ce090dd92dc2/disk-89748acd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/32b5903a7759/vmlinux-89748acd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dc68a867773d/bzImage-89748acd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9a4fbb77c9d4aacd3388@syzkaller.appspotmail.com

tipc: Started in network mode
tipc: Node identity 4689370d27fe, cluster identity 4711
tipc: Enabled bearer <eth:syzkaller0>, priority 0
=====================================================
BUG: KMSAN: uninit-value in tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_l2_rcv_msg+0x213/0x320 net/tipc/bearer.c:668
 __netif_receive_skb_list_ptype net/core/dev.c:6027 [inline]
 __netif_receive_skb_list_core+0x133b/0x16b0 net/core/dev.c:6069
 __netif_receive_skb_list net/core/dev.c:6121 [inline]
 netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6212
 gro_normal_list include/net/gro.h:532 [inline]
 gro_flush_normal include/net/gro.h:540 [inline]
 napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6581
 napi_complete include/linux/netdevice.h:589 [inline]
 tun_get_user+0x4c0d/0x6ca0 drivers/net/tun.c:1921
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 do_iter_readv_writev+0x947/0xba0 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
 x64_sys_call+0x24b1/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4186 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_node_noprof+0x818/0xf00 mm/slub.c:4281
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:578
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:669
 napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:811
 napi_get_frags+0xab/0x250 net/core/gro.c:673
 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
 tun_get_user+0x134f/0x6ca0 drivers/net/tun.c:1784
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 do_iter_readv_writev+0x947/0xba0 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
 x64_sys_call+0x24b1/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5808 Comm: syz-executor123 Not tainted 6.16.0-syzkaller-10499-g89748acdf226 #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

Forwarded: [PATCH net] net/core : fix KMSAN: uninit value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH net] net/core : fix KMSAN: uninit value in tipc_rcv
Author: hariconscious@gmail.com

From: HariKrishna Sagala <hariconscious@gmail.com>

syzbot KMSAN points to the unint value in the socket buffer creation.
In the skbuff.c, kmalloc_reserve API takes gfp flags option, appended the
flag "GFP_ZERO" to the existing flags to get the zeroed buffer.

Reported-by:syzbot+9a4fbb77c9d4aacd3388@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
Signed-off-by: HariKrishna Sagala <hariconscious@gmail.com>
---

#syz test

 net/core/skbuff.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ee0274417948..2308ebf99bbd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -573,6 +573,7 @@ static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
 	void *obj;
 
 	obj_size = SKB_HEAD_ALIGN(*size);
+	flags |= __GFP_ZERO;
 	if (obj_size <= SKB_SMALL_HEAD_CACHE_SIZE &&
 	    !(flags & KMALLOC_NOT_NORMAL_BITS)) {
 		obj = kmem_cache_alloc_node(net_hotdata.skb_small_head_cache,
-- 
2.43.0

Forwarded: [PATCH v2 net] net/core : fix KMSAN: uninit value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH v2 net] net/core : fix KMSAN: uninit value in tipc_rcv
Author: hariconscious@gmail.com

From: HariKrishna Sagala <hariconscious@gmail.com>

---

#syz test

diff --git a/net/tipc/node.c b/net/tipc/node.c
index a07fb073368c..f64f653e775a 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -2117,6 +2117,8 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 		goto discard;
 	__skb_queue_head_init(&xmitq);
 	hdr = buf_msg(skb);
+	if(!hdr)
+		return -EINVAL;
 	usr = msg_user(hdr);
 	bc_ack = msg_bcast_ack(hdr);
 

Forwarded: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv
Author: hariconscious@gmail.com

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..144b02534196 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -69,6 +69,7 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)
 {
        struct sk_buff *skb;

+       gfp |= __GFP_ZERO;
        skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
        if (skb) {
                skb_reserve(skb, BUF_HEADROOM);

Forwarded: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv
Author: hariconscious@gmail.com

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..eb50a9e23507 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -71,6 +71,8 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)

        skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
        if (skb) {
+               pr_info("tipc_buf_acquire\n");
+               memset(skb, 0, sizeof(struct sk_buff));
                skb_reserve(skb, BUF_HEADROOM);
                skb_put(skb, size);
                skb->next = NULL;

Forwarded: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv
Author: hariconscious@gmail.com

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..4c22cce4be30 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -71,6 +71,8 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)

        skb = alloc_skb_fclone(BUF_OVERHEAD + size, gfp);
        if (skb) {
+               pr_info("tipc_buf_acquire data len: %d\n", skb->data_len);
+               memset(skb->data, 0, skb->data_len);
                skb_reserve(skb, BUF_HEADROOM);
                skb_put(skb, size);
                skb->next = NULL;

Forwarded: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv
Author: hariconscious@gmail.com

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..ecfafb363a99 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -73,6 +73,7 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)
        if (skb) {
                skb_reserve(skb, BUF_HEADROOM);
                skb_put(skb, size);
+               skb_put_zero(skb, BUF_OVERHEAD + size);
                skb->next = NULL;
        }
        return skb;

Forwarded: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [PATCH] net: core: fix KMSAN: unint value in tipc_rcv
Author: hariconscious@gmail.com

#syz test

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index 76284fc538eb..1f2a939d341c 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -73,6 +73,7 @@ struct sk_buff *tipc_buf_acquire(u32 size, gfp_t gfp)
        if (skb) {
                skb_reserve(skb, BUF_HEADROOM);
                skb_put(skb, size);
+               memset(skb->data, 0, size);
                skb->next = NULL;
        }
        return skb;