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linux/net/l2tp
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James Chapman d587d82542 l2tp: make session IDR and tunnel session list coherent 
Modify l2tp_session_register and l2tp_session_unhash so that the
session IDR and tunnel session lists remain coherent. To do so, hold
the session IDR lock and the tunnel's session list lock when making
any changes to either list.

Without this change, a rare race condition could hit the WARN_ON_ONCE
in l2tp_session_unhash if a thread replaced the IDR entry while
another thread was registering the same ID.

 [ 7126.151795][T17511] WARNING: CPU: 3 PID: 17511 at net/l2tp/l2tp_core.c:1282 l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.163754][T17511]  ? show_regs+0x93/0xa0
 [ 7126.164157][T17511]  ? __warn+0xe5/0x3c0
 [ 7126.164536][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.165070][T17511]  ? report_bug+0x2e1/0x500
 [ 7126.165486][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.166013][T17511]  ? handle_bug+0x99/0x130
 [ 7126.166428][T17511]  ? exc_invalid_op+0x35/0x80
 [ 7126.166890][T17511]  ? asm_exc_invalid_op+0x1a/0x20
 [ 7126.167372][T17511]  ? l2tp_session_delete.part.0+0x87d/0xbc0
 [ 7126.167900][T17511]  ? l2tp_session_delete.part.0+0x87e/0xbc0
 [ 7126.168429][T17511]  ? __local_bh_enable_ip+0xa4/0x120
 [ 7126.168917][T17511]  l2tp_session_delete+0x40/0x50
 [ 7126.169369][T17511]  pppol2tp_release+0x1a1/0x3f0
 [ 7126.169817][T17511]  __sock_release+0xb3/0x270
 [ 7126.170247][T17511]  ? __pfx_sock_close+0x10/0x10
 [ 7126.170697][T17511]  sock_close+0x1c/0x30
 [ 7126.171087][T17511]  __fput+0x40b/0xb90
 [ 7126.171470][T17511]  task_work_run+0x16c/0x260
 [ 7126.171897][T17511]  ? __pfx_task_work_run+0x10/0x10
 [ 7126.172362][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.172863][T17511]  ? do_raw_spin_unlock+0x174/0x230
 [ 7126.173348][T17511]  do_exit+0xaae/0x2b40
 [ 7126.173730][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.174235][T17511]  ? __pfx_lock_release+0x10/0x10
 [ 7126.174690][T17511]  ? srso_alias_return_thunk+0x5/0xfbef5
 [ 7126.175190][T17511]  ? do_raw_spin_lock+0x12c/0x2b0
 [ 7126.175650][T17511]  ? __pfx_do_exit+0x10/0x10
 [ 7126.176072][T17511]  ? _raw_spin_unlock_irq+0x23/0x50
 [ 7126.176543][T17511]  do_group_exit+0xd3/0x2a0
 [ 7126.176990][T17511]  __x64_sys_exit_group+0x3e/0x50
 [ 7126.177456][T17511]  x64_sys_call+0x1821/0x1830
 [ 7126.177895][T17511]  do_syscall_64+0xcb/0x250
 [ 7126.178317][T17511]  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: aa5e17e1f5 ("l2tp: store l2tpv3 sessions in per-net IDR")
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: Tom Parkin <tparkin@katalix.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240718134348.289865-1-jchapman@katalix.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-07-23 11:24:46 +02:00
..
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
l2tp_core.c l2tp: make session IDR and tunnel session list coherent 2024-07-23 11:24:46 +02:00
l2tp_core.h l2tp: replace hlist with simple list for per-tunnel session list 2024-06-21 11:33:34 +01:00
l2tp_debugfs.c l2tp: replace hlist with simple list for per-tunnel session list 2024-06-21 11:33:34 +01:00
l2tp_eth.c net l2tp: drop flow hash on forward 2024-04-26 13:48:24 +02:00
l2tp_ip.c l2tp: store l2tpv3 sessions in per-net IDR 2024-06-21 11:33:33 +01:00
l2tp_ip6.c l2tp: store l2tpv3 sessions in per-net IDR 2024-06-21 11:33:33 +01:00
l2tp_netlink.c l2tp: use IDR for all session lookups 2024-06-21 11:33:34 +01:00
l2tp_ppp.c l2tp: use IDR for all session lookups 2024-06-21 11:33:34 +01:00
Makefile l2tp: add tracepoint infrastructure to core 2020-08-22 12:44:37 -07:00
trace.h l2tp: add tracepoint definitions in trace.h 2020-08-22 12:44:37 -07:00