[PATCH OLK-6.6 0/2] pptp: Fix skb length handling and error path in pptp_xmit()
*** BLURB HERE *** Eric Dumazet (2): pptp: ensure minimal skb length in pptp_xmit() pptp: fix pptp_xmit() error path drivers/net/ppp/pptp.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) -- 2.34.1
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From: Eric Dumazet <edumazet@google.com> stable inclusion from stable-v6.6.102 commit 5005d24377378a20e5c0e53052fc4ebdcdcbc611 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICU6H0 CVE: CVE-2025-38574 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit de9c4861fb42f0cd72da844c3c34f692d5895b7b ] Commit aabc6596ffb3 ("net: ppp: Add bound checking for skb data on ppp_sync_txmung") fixed ppp_sync_txmunge() We need a similar fix in pptp_xmit(), otherwise we might read uninit data as reported by syzbot. BUG: KMSAN: uninit-value in pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2290 [inline] ppp_input+0x1d6/0xe60 drivers/net/ppp/ppp_generic.c:2314 pppoe_rcv_core+0x1e8/0x760 drivers/net/ppp/pppoe.c:379 sk_backlog_rcv+0x142/0x420 include/net/sock.h:1148 __release_sock+0x1d3/0x330 net/core/sock.c:3213 release_sock+0x6b/0x270 net/core/sock.c:3767 pppoe_sendmsg+0x15d/0xcb0 drivers/net/ppp/pppoe.c:904 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x330/0x3d0 net/socket.c:727 ____sys_sendmsg+0x893/0xd80 net/socket.c:2566 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2620 __sys_sendmmsg+0x2d9/0x7c0 net/socket.c:2709 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+afad90ffc8645324afe5@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/68887d86.a00a0220.b12ec.00cd.GAE@google.com/T... Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Dawid Osuchowski <dawid.osuchowski@linux.intel.com> Link: https://patch.msgid.link/20250729080207.1863408-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Jiacheng Yu <yujiacheng3@huawei.com> --- drivers/net/ppp/pptp.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c index 6833ef0c7930..4455d99be767 100644 --- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -159,9 +159,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) int len; unsigned char *data; __u32 seq_recv; - - - struct rtable *rt; + struct rtable *rt = NULL; struct net_device *tdev; struct iphdr *iph; int max_headroom; @@ -179,16 +177,20 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); - if (!new_skb) { - ip_rt_put(rt); + + if (!new_skb) goto tx_error; - } + if (skb->sk) skb_set_owner_w(new_skb, skb->sk); consume_skb(skb); skb = new_skb; } + /* Ensure we can safely access protocol field and LCP code */ + if (!pskb_may_pull(skb, 3)) + goto tx_error; + data = skb->data; islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7; @@ -262,6 +264,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) return 1; tx_error: + ip_rt_put(rt); kfree_skb(skb); return 1; } -- 2.34.1
From: Eric Dumazet <edumazet@google.com> stable inclusion from stable-v6.6.102 commit bd7f84df5436ca30a0f75e5a89e2952ec3814de0 category: bugifx bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICU6H0 CVE: CVE-2025-38574 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit ae633388cae349886f1a3cfb27aa092854b24c1b ] I accidentally added a bug in pptp_xmit() that syzbot caught for us. Only call ip_rt_put() if a route has been allocated. BUG: unable to handle page fault for address: ffffffffffffffdb PGD df3b067 P4D df3b067 PUD df3d067 PMD 0 Oops: Oops: 0002 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 6346 Comm: syz.0.336 Not tainted 6.16.0-next-20250804-syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:arch_atomic_add_return arch/x86/include/asm/atomic.h:85 [inline] RIP: 0010:raw_atomic_sub_return_release include/linux/atomic/atomic-arch-fallback.h:846 [inline] RIP: 0010:atomic_sub_return_release include/linux/atomic/atomic-instrumented.h:327 [inline] RIP: 0010:__rcuref_put include/linux/rcuref.h:109 [inline] RIP: 0010:rcuref_put+0x172/0x210 include/linux/rcuref.h:173 Call Trace: <TASK> dst_release+0x24/0x1b0 net/core/dst.c:167 ip_rt_put include/net/route.h:285 [inline] pptp_xmit+0x14b/0x1a90 drivers/net/ppp/pptp.c:267 __ppp_channel_push+0xf2/0x1c0 drivers/net/ppp/ppp_generic.c:2166 ppp_channel_push+0x123/0x660 drivers/net/ppp/ppp_generic.c:2198 ppp_write+0x2b0/0x400 drivers/net/ppp/ppp_generic.c:544 vfs_write+0x27b/0xb30 fs/read_write.c:684 ksys_write+0x145/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: de9c4861fb42 ("pptp: ensure minimal skb length in pptp_xmit()") Reported-by: syzbot+27d7cfbc93457e472e00@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/689095a5.050a0220.1fc43d.0009.GAE@google.com/ Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://patch.msgid.link/20250807142146.2877060-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Jiacheng Yu <yujiacheng3@huawei.com> --- drivers/net/ppp/pptp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c index 4455d99be767..3a10303eb756 100644 --- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -159,17 +159,17 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) int len; unsigned char *data; __u32 seq_recv; - struct rtable *rt = NULL; + struct rtable *rt; struct net_device *tdev; struct iphdr *iph; int max_headroom; if (sk_pppox(po)->sk_state & PPPOX_DEAD) - goto tx_error; + goto tx_drop; rt = pptp_route_output(po, &fl4); if (IS_ERR(rt)) - goto tx_error; + goto tx_drop; tdev = rt->dst.dev; @@ -265,6 +265,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) tx_error: ip_rt_put(rt); +tx_drop: kfree_skb(skb); return 1; } -- 2.34.1
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