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Filename Latest commit message Latest commit date
Eric Dumazet d05c2fdf8e tcp: tcp_rtx_synack() can be called from process context
[ Upstream commit 0a375c822497ed6ad6b5da0792a12a6f1af10c0b ]

Laurent reported the enclosed report [1]

This bug triggers with following coditions:

0) Kernel built with CONFIG_DEBUG_PREEMPT=y

1) A new passive FastOpen TCP socket is created.
   This FO socket waits for an ACK coming from client to be a complete
   ESTABLISHED one.
2) A socket operation on this socket goes through lock_sock()
   release_sock() dance.
3) While the socket is owned by the user in step 2),
   a retransmit of the SYN is received and stored in socket backlog.
4) At release_sock() time, the socket backlog is processed while
   in process context.
5) A SYNACK packet is cooked in response of the SYN retransmit.
6) -> tcp_rtx_synack() is called in process context.

Before blamed commit, tcp_rtx_synack() was always called from BH handler,
from a timer handler.

Fix this by using TCP_INC_STATS() & NET_INC_STATS()
which do not assume caller is in non preemptible context.

[1]
BUG: using __this_cpu_add() in preemptible [00000000] code: epollpep/2180
caller is tcp_rtx_synack.part.0+0x36/0xc0
CPU: 10 PID: 2180 Comm: epollpep Tainted: G           OE     5.16.0-0.bpo.4-amd64 #1  Debian 5.16.12-1~bpo11+1
Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021
Call Trace:
 <TASK>
 dump_stack_lvl+0x48/0x5e
 check_preemption_disabled+0xde/0xe0
 tcp_rtx_synack.part.0+0x36/0xc0
 tcp_rtx_synack+0x8d/0xa0
 ? kmem_cache_alloc+0x2e0/0x3e0
 ? apparmor_file_alloc_security+0x3b/0x1f0
 inet_rtx_syn_ack+0x16/0x30
 tcp_check_req+0x367/0x610
 tcp_rcv_state_process+0x91/0xf60
 ? get_nohz_timer_target+0x18/0x1a0
 ? lock_timer_base+0x61/0x80
 ? preempt_count_add+0x68/0xa0
 tcp_v4_do_rcv+0xbd/0x270
 __release_sock+0x6d/0xb0
 release_sock+0x2b/0x90
 sock_setsockopt+0x138/0x1140
 ? __sys_getsockname+0x7e/0xc0
 ? aa_sk_perm+0x3e/0x1a0
 __sys_setsockopt+0x198/0x1e0
 __x64_sys_setsockopt+0x21/0x30
 do_syscall_64+0x38/0xc0
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 168a8f5805 ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Laurent Fasnacht <laurent.fasnacht@proton.ch>
Acked-by: Neal Cardwell <ncardwell@google.com>
Link: https://lore.kernel.org/r/20220530213713.601888-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-06-14 18:11:55 +02:00
arch s390/crypto: fix scatterwalk_unmap() callers in AES-GCM 2022-06-14 18:11:54 +02:00
block block: fix bio_clone_blkg_association() to associate with proper blkcg_gq 2022-06-14 18:11:50 +02:00
certs
crypto crypto: cryptd - Protect per-CPU resource by disabling BH. 2022-06-14 18:11:41 +02:00
Documentation dt-bindings: gpio: altera: correct interrupt-cells 2022-06-14 18:11:49 +02:00
drivers net/mlx5e: Update netdev features after changing XDP state 2022-06-14 18:11:55 +02:00
fs jffs2: fix memory leak in jffs2_do_fill_super 2022-06-14 18:11:55 +02:00
include net: sched: add barrier to fix packet stuck problem for lockless qdisc 2022-06-14 18:11:55 +02:00
init Kconfig: add config option for asm goto w/ outputs 2022-06-14 18:11:50 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-14 18:11:41 +02:00
kernel tracing: Fix potential double free in create_var_ref() 2022-06-14 18:11:46 +02:00
lib assoc_array: Fix BUG_ON during garbage collect 2022-06-06 08:33:50 +02:00
LICENSES
mm hugetlb: fix huge_pmd_unshare address update 2022-06-14 18:11:48 +02:00
net tcp: tcp_rtx_synack() can be called from process context 2022-06-14 18:11:55 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts modpost: fix removing numeric suffixes 2022-06-14 18:11:55 +02:00
security efi: Do not import certificates from UEFI Secure Boot for T2 Macs 2022-06-14 18:11:44 +02:00
sound ASoC: fsl_sai: Fix FSL_SAI_xDR/xFR definition 2022-06-14 18:11:54 +02:00
tools perf jevents: Fix event syntax error caused by ExtSel 2022-06-14 18:11:44 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
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.gitignore
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Makefile Linux 5.4.197 2022-06-06 08:33:51 +02:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.