linux-stable.git/net/sctp, branch linux-6.13.y

sctp: detect and prevent references to a freed transport in sendmsg

2025-04-20T08:18:18+00:00

commit f1a69a940de58b16e8249dff26f74c8cc59b32be upstream.

sctp_sendmsg() re-uses associations and transports when possible by
doing a lookup based on the socket endpoint and the message destination
address, and then sctp_sendmsg_to_asoc() sets the selected transport in
all the message chunks to be sent.

There's a possible race condition if another thread triggers the removal
of that selected transport, for instance, by explicitly unbinding an
address with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have
been set up and before the message is sent. This can happen if the send
buffer is full, during the period when the sender thread temporarily
releases the socket lock in sctp_wait_for_sndbuf().

This causes the access to the transport data in
sctp_outq_select_transport(), when the association outqueue is flushed,
to result in a use-after-free read.

This change avoids this scenario by having sctp_transport_free() signal
the freeing of the transport, tagging it as "dead". In order to do this,
the patch restores the "dead" bit in struct sctp_transport, which was
removed in
commit 47faa1e4c50e ("sctp: remove the dead field of sctp_transport").

Then, in the scenario where the sender thread has released the socket
lock in sctp_wait_for_sndbuf(), the bit is checked again after
re-acquiring the socket lock to detect the deletion. This is done while
holding a reference to the transport to prevent it from being freed in
the process.

If the transport was deleted while the socket lock was relinquished,
sctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the
send.

The bug was found by a private syzbot instance (see the error report [1]
and the C reproducer that triggers it [2]).

Link: https://people.igalia.com/rcn/kernel_logs/20250402__KASAN_slab-use-after-free_Read_in_sctp_outq_select_transport.txt [1]
Link: https://people.igalia.com/rcn/kernel_logs/20250402__KASAN_slab-use-after-free_Read_in_sctp_outq_select_transport__repro.c [2]
Cc: stable@vger.kernel.org
Fixes: df132eff4638 ("sctp: clear the transport of some out_chunk_list chunks in sctp_assoc_rm_peer")
Suggested-by: Xin Long 
Signed-off-by: Ricardo Cañuelo Navarro 
Acked-by: Xin Long 
Link: https://patch.msgid.link/20250404-kasan_slab-use-after-free_read_in_sctp_outq_select_transport__20250404-v1-1-5ce4a0b78ef2@igalia.com
Signed-off-by: Paolo Abeni 
Signed-off-by: Greg Kroah-Hartman

sctp: add mutual exclusion in proc_sctp_do_udp_port()

2025-04-10T12:41:59+00:00

[ Upstream commit 10206302af856791fbcc27a33ed3c3eb09b2793d ]

We must serialize calls to sctp_udp_sock_stop() and sctp_udp_sock_start()
or risk a crash as syzbot reported:

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 1 UID: 0 PID: 6551 Comm: syz.1.44 Not tainted 6.14.0-syzkaller-g7f2ff7b62617 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
 RIP: 0010:kernel_sock_shutdown+0x47/0x70 net/socket.c:3653
Call Trace:
 
  udp_tunnel_sock_release+0x68/0x80 net/ipv4/udp_tunnel_core.c:181
  sctp_udp_sock_stop+0x71/0x160 net/sctp/protocol.c:930
  proc_sctp_do_udp_port+0x264/0x450 net/sctp/sysctl.c:553
  proc_sys_call_handler+0x3d0/0x5b0 fs/proc/proc_sysctl.c:601
  iter_file_splice_write+0x91c/0x1150 fs/splice.c:738
  do_splice_from fs/splice.c:935 [inline]
  direct_splice_actor+0x18f/0x6c0 fs/splice.c:1158
  splice_direct_to_actor+0x342/0xa30 fs/splice.c:1102
  do_splice_direct_actor fs/splice.c:1201 [inline]
  do_splice_direct+0x174/0x240 fs/splice.c:1227
  do_sendfile+0xafd/0xe50 fs/read_write.c:1368
  __do_sys_sendfile64 fs/read_write.c:1429 [inline]
  __se_sys_sendfile64 fs/read_write.c:1415 [inline]
  __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1415
  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]

Fixes: 046c052b475e ("sctp: enable udp tunneling socks")
Reported-by: syzbot+fae49d997eb56fa7c74d@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/67ea5c01.050a0220.1547ec.012b.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet 
Cc: Marcelo Ricardo Leitner 
Acked-by: Xin Long 
Link: https://patch.msgid.link/20250331091532.224982-1-edumazet@google.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

sctp: Fix undefined behavior in left shift operation

2025-03-22T19:56:50+00:00

[ Upstream commit 606572eb22c1786a3957d24307f5760bb058ca19 ]

According to the C11 standard (ISO/IEC 9899:2011, 6.5.7):
"If E1 has a signed type and E1 x 2^E2 is not representable in the result
type, the behavior is undefined."

Shifting 1 << 31 causes signed integer overflow, which leads to undefined
behavior.

Fix this by explicitly using '1U << 31' to ensure the shift operates on
an unsigned type, avoiding undefined behavior.

Signed-off-by: Yu-Chun Lin 
Link: https://patch.msgid.link/20250218081217.3468369-1-eleanor15x@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

sctp: sysctl: plpmtud_probe_interval: avoid using current->nsproxy

2025-01-09T16:53:35+00:00

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.probe_interval' is
used.

Fixes: d1e462a7a5f3 ("sctp: add probe_interval in sysctl and sock/asoc/transport")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1]
Suggested-by: Al Viro 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-8-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski

sctp: sysctl: udp_port: avoid using current->nsproxy

2025-01-09T16:53:35+00:00

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, but that would
increase the size of this fix, while 'sctp.ctl_sock' still needs to be
retrieved from 'net' structure.

Fixes: 046c052b475e ("sctp: enable udp tunneling socks")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1]
Suggested-by: Al Viro 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-7-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski

sctp: sysctl: auth_enable: avoid using current->nsproxy

2025-01-09T16:53:35+00:00

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, but that would
increase the size of this fix, while 'sctp.ctl_sock' still needs to be
retrieved from 'net' structure.

Fixes: b14878ccb7fa ("net: sctp: cache auth_enable per endpoint")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1]
Suggested-by: Al Viro 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-6-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski

sctp: sysctl: rto_min/max: avoid using current->nsproxy

2025-01-09T16:53:34+00:00

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.rto_min/max' is used.

Fixes: 4f3fdf3bc59c ("sctp: add check rto_min and rto_max in sysctl")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1]
Suggested-by: Al Viro 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-5-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski

sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy

2025-01-09T16:53:34+00:00

As mentioned in a previous commit of this series, using the 'net'
structure via 'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.sctp_hmac_alg' is
used.

Fixes: 3c68198e7511 ("sctp: Make hmac algorithm selection for cookie generation dynamic")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com [1]
Suggested-by: Al Viro 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-4-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski

net/sctp: Prevent autoclose integer overflow in sctp_association_init()

2024-12-23T18:10:13+00:00

While by default max_autoclose equals to INT_MAX / HZ, one may set
net.sctp.max_autoclose to UINT_MAX. There is code in
sctp_association_init() that can consequently trigger overflow.

Cc: stable@vger.kernel.org
Fixes: 9f70f46bd4c7 ("sctp: properly latch and use autoclose value from sock to association")
Signed-off-by: Nikolay Kuratov 
Acked-by: Xin Long 
Link: https://patch.msgid.link/20241219162114.2863827-1-kniv@yandex-team.ru
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2024-11-14T19:29:15+00:00

Cross-merge networking fixes after downstream PR (net-6.12-rc8).

Conflicts:

tools/testing/selftests/net/.gitignore
  252e01e68241 ("selftests: net: add netlink-dumps to .gitignore")
  be43a6b23829 ("selftests: ncdevmem: Move ncdevmem under drivers/net/hw")
https://lore.kernel.org/all/20241113122359.1b95180a@canb.auug.org.au/

drivers/net/phy/phylink.c
  671154f174e0 ("net: phylink: ensure PHY momentary link-fails are handled")
  7530ea26c810 ("net: phylink: remove "using_mac_select_pcs"")

Adjacent changes:

drivers/net/ethernet/stmicro/stmmac/dwmac-intel-plat.c
  5b366eae7193 ("stmmac: dwmac-intel-plat: fix call balance of tx_clk handling routines")
  e96321fad3ad ("net: ethernet: Switch back to struct platform_driver::remove()")

Signed-off-by: Jakub Kicinski