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Kuniyuki Iwashima f2db7230f7 tcp: Use refcount_inc_not_zero() in tcp_twsk_unique(). 
Anderson Nascimento reported a use-after-free splat in tcp_twsk_unique()
with nice analysis.

Since commit ec94c2696f ("tcp/dccp: avoid one atomic operation for
timewait hashdance"), inet_twsk_hashdance() sets TIME-WAIT socket's
sk_refcnt after putting it into ehash and releasing the bucket lock.

Thus, there is a small race window where other threads could try to
reuse the port during connect() and call sock_hold() in tcp_twsk_unique()
for the TIME-WAIT socket with zero refcnt.

If that happens, the refcnt taken by tcp_twsk_unique() is overwritten
and sock_put() will cause underflow, triggering a real use-after-free
somewhere else.

To avoid the use-after-free, we need to use refcount_inc_not_zero() in
tcp_twsk_unique() and give up on reusing the port if it returns false.

[0]:
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 1039313 at lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110
CPU: 0 PID: 1039313 Comm: trigger Not tainted 6.8.6-200.fc39.x86_64 #1
Hardware name: VMware, Inc. VMware20,1/440BX Desktop Reference Platform, BIOS VMW201.00V.21805430.B64.2305221830 05/22/2023
RIP: 0010:refcount_warn_saturate+0xe5/0x110
Code: 42 8e ff 0f 0b c3 cc cc cc cc 80 3d aa 13 ea 01 00 0f 85 5e ff ff ff 48 c7 c7 f8 8e b7 82 c6 05 96 13 ea 01 01 e8 7b 42 8e ff <0f> 0b c3 cc cc cc cc 48 c7 c7 50 8f b7 82 c6 05 7a 13 ea 01 01 e8
RSP: 0018:ffffc90006b43b60 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff888009bb3ef0 RCX: 0000000000000027
RDX: ffff88807be218c8 RSI: 0000000000000001 RDI: ffff88807be218c0
RBP: 0000000000069d70 R08: 0000000000000000 R09: ffffc90006b439f0
R10: ffffc90006b439e8 R11: 0000000000000003 R12: ffff8880029ede84
R13: 0000000000004e20 R14: ffffffff84356dc0 R15: ffff888009bb3ef0
FS:  00007f62c10926c0(0000) GS:ffff88807be00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020ccb000 CR3: 000000004628c005 CR4: 0000000000f70ef0
PKRU: 55555554
Call Trace:
 <TASK>
 ? refcount_warn_saturate+0xe5/0x110
 ? __warn+0x81/0x130
 ? refcount_warn_saturate+0xe5/0x110
 ? report_bug+0x171/0x1a0
 ? refcount_warn_saturate+0xe5/0x110
 ? handle_bug+0x3c/0x80
 ? exc_invalid_op+0x17/0x70
 ? asm_exc_invalid_op+0x1a/0x20
 ? refcount_warn_saturate+0xe5/0x110
 tcp_twsk_unique+0x186/0x190
 __inet_check_established+0x176/0x2d0
 __inet_hash_connect+0x74/0x7d0
 ? __pfx___inet_check_established+0x10/0x10
 tcp_v4_connect+0x278/0x530
 __inet_stream_connect+0x10f/0x3d0
 inet_stream_connect+0x3a/0x60
 __sys_connect+0xa8/0xd0
 __x64_sys_connect+0x18/0x20
 do_syscall_64+0x83/0x170
 entry_SYSCALL_64_after_hwframe+0x78/0x80
RIP: 0033:0x7f62c11a885d
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a3 45 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007f62c1091e58 EFLAGS: 00000296 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000020ccb004 RCX: 00007f62c11a885d
RDX: 0000000000000010 RSI: 0000000020ccb000 RDI: 0000000000000003
RBP: 00007f62c1091e90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 00007f62c10926c0
R13: ffffffffffffff88 R14: 0000000000000000 R15: 00007ffe237885b0
 </TASK>

Fixes: ec94c2696f ("tcp/dccp: avoid one atomic operation for timewait hashdance")
Reported-by: Anderson Nascimento <anderson@allelesecurity.com>
Closes: https://lore.kernel.org/netdev/37a477a6-d39e-486b-9577-3463f655a6b7@allelesecurity.com/
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240501213145.62261-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
History 2024-05-02 19:02:46 -07:00
arch Including fixes from bpf. 2024-05-02 08:51:47 -07:00
block vfs-6.9-rc6.fixes 2024-04-26 11:01:28 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
Documentation Pin control fixes for the v6.9 series: 2024-04-30 08:50:58 -07:00
drivers Including fixes from bpf. 2024-05-02 08:51:47 -07:00
fs nfsd-6.9 fixes: 2024-04-29 14:22:24 -07:00
include Including fixes from bpf. 2024-05-02 08:51:47 -07:00
init Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
io_uring io_uring/net: restore msg_control on sendzc retry 2024-04-08 21:48:41 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel Including fixes from bpf. 2024-05-02 08:51:47 -07:00
lib Including fixes from bpf. 2024-05-02 08:51:47 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() 2024-04-25 10:07:27 -07:00
net tcp: Use refcount_inc_not_zero() in tcp_twsk_unique(). 2024-05-02 19:02:46 -07:00
rust rust: remove params from module macro example 2024-04-25 17:34:33 +02:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
security security: Place security_path_post_mknod() where the original IMA call was 2024-04-03 10:21:32 -07:00
sound ALSA: seq: ump: Fix conversion from MIDI2 to MIDI1 UMP messages 2024-04-19 12:07:14 +02:00
tools Including fixes from bpf. 2024-05-02 08:51:47 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start() 2024-04-11 12:58:53 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap bpf-for-netdev 2024-04-26 17:36:53 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Including fixes from bpf. 2024-05-02 08:51:47 -07:00
Makefile Linux 6.9-rc6 2024-04-28 13:47:24 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.