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Kuniyuki Iwashima 807067bf01 kcm: Serialise kcm_sendmsg() for the same socket. 
syzkaller reported UAF in kcm_release(). [0]

The scenario is

  1. Thread A builds a skb with MSG_MORE and sets kcm->seq_skb.

  2. Thread A resumes building skb from kcm->seq_skb but is blocked
     by sk_stream_wait_memory()

  3. Thread B calls sendmsg() concurrently, finishes building kcm->seq_skb
     and puts the skb to the write queue

  4. Thread A faces an error and finally frees skb that is already in the
     write queue

  5. kcm_release() does double-free the skb in the write queue

When a thread is building a MSG_MORE skb, another thread must not touch it.

Let's add a per-sk mutex and serialise kcm_sendmsg().

[0]:
BUG: KASAN: slab-use-after-free in __skb_unlink include/linux/skbuff.h:2366 [inline]
BUG: KASAN: slab-use-after-free in __skb_dequeue include/linux/skbuff.h:2385 [inline]
BUG: KASAN: slab-use-after-free in __skb_queue_purge_reason include/linux/skbuff.h:3175 [inline]
BUG: KASAN: slab-use-after-free in __skb_queue_purge include/linux/skbuff.h:3181 [inline]
BUG: KASAN: slab-use-after-free in kcm_release+0x170/0x4c8 net/kcm/kcmsock.c:1691
Read of size 8 at addr ffff0000ced0fc80 by task syz-executor329/6167

CPU: 1 PID: 6167 Comm: syz-executor329 Tainted: G    B              6.8.0-rc5-syzkaller-g9abbc24128bc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:291
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:298
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x178/0x518 mm/kasan/report.c:488
 kasan_report+0xd8/0x138 mm/kasan/report.c:601
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 __skb_unlink include/linux/skbuff.h:2366 [inline]
 __skb_dequeue include/linux/skbuff.h:2385 [inline]
 __skb_queue_purge_reason include/linux/skbuff.h:3175 [inline]
 __skb_queue_purge include/linux/skbuff.h:3181 [inline]
 kcm_release+0x170/0x4c8 net/kcm/kcmsock.c:1691
 __sock_release net/socket.c:659 [inline]
 sock_close+0xa4/0x1e8 net/socket.c:1421
 __fput+0x30c/0x738 fs/file_table.c:376
 ____fput+0x20/0x30 fs/file_table.c:404
 task_work_run+0x230/0x2e0 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x618/0x1f64 kernel/exit.c:871
 do_group_exit+0x194/0x22c kernel/exit.c:1020
 get_signal+0x1500/0x15ec kernel/signal.c:2893
 do_signal+0x23c/0x3b44 arch/arm64/kernel/signal.c:1249
 do_notify_resume+0x74/0x1f4 arch/arm64/kernel/entry-common.c:148
 exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
 el0_svc+0xac/0x168 arch/arm64/kernel/entry-common.c:713
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

Allocated by task 6166:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_alloc_info+0x70/0x84 mm/kasan/generic.c:626
 unpoison_slab_object mm/kasan/common.c:314 [inline]
 __kasan_slab_alloc+0x74/0x8c mm/kasan/common.c:340
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3813 [inline]
 slab_alloc_node mm/slub.c:3860 [inline]
 kmem_cache_alloc_node+0x204/0x4c0 mm/slub.c:3903
 __alloc_skb+0x19c/0x3d8 net/core/skbuff.c:641
 alloc_skb include/linux/skbuff.h:1296 [inline]
 kcm_sendmsg+0x1d3c/0x2124 net/kcm/kcmsock.c:783
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 sock_sendmsg+0x220/0x2c0 net/socket.c:768
 splice_to_socket+0x7cc/0xd58 fs/splice.c:889
 do_splice_from fs/splice.c:941 [inline]
 direct_splice_actor+0xec/0x1d8 fs/splice.c:1164
 splice_direct_to_actor+0x438/0xa0c fs/splice.c:1108
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0x1e4/0x304 fs/splice.c:1233
 do_sendfile+0x460/0xb3c fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __arm64_sys_sendfile64+0x160/0x3b4 fs/read_write.c:1348
 __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

Freed by task 6167:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_free_info+0x5c/0x74 mm/kasan/generic.c:640
 poison_slab_object+0x124/0x18c mm/kasan/common.c:241
 __kasan_slab_free+0x3c/0x78 mm/kasan/common.c:257
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2121 [inline]
 slab_free mm/slub.c:4299 [inline]
 kmem_cache_free+0x15c/0x3d4 mm/slub.c:4363
 kfree_skbmem+0x10c/0x19c
 __kfree_skb net/core/skbuff.c:1109 [inline]
 kfree_skb_reason+0x240/0x6f4 net/core/skbuff.c:1144
 kfree_skb include/linux/skbuff.h:1244 [inline]
 kcm_release+0x104/0x4c8 net/kcm/kcmsock.c:1685
 __sock_release net/socket.c:659 [inline]
 sock_close+0xa4/0x1e8 net/socket.c:1421
 __fput+0x30c/0x738 fs/file_table.c:376
 ____fput+0x20/0x30 fs/file_table.c:404
 task_work_run+0x230/0x2e0 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x618/0x1f64 kernel/exit.c:871
 do_group_exit+0x194/0x22c kernel/exit.c:1020
 get_signal+0x1500/0x15ec kernel/signal.c:2893
 do_signal+0x23c/0x3b44 arch/arm64/kernel/signal.c:1249
 do_notify_resume+0x74/0x1f4 arch/arm64/kernel/entry-common.c:148
 exit_to_user_mode_prepare arch/arm64/kernel/entry-common.c:169 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:178 [inline]
 el0_svc+0xac/0x168 arch/arm64/kernel/entry-common.c:713
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

The buggy address belongs to the object at ffff0000ced0fc80
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 0 bytes inside of
 freed 240-byte region [ffff0000ced0fc80, ffff0000ced0fd70)

The buggy address belongs to the physical page:
page:00000000d35f4ae4 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ed0f
flags: 0x5ffc00000000800(slab|node=0|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 05ffc00000000800 ffff0000c1cbf640 fffffdffc3423100 dead000000000004
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000ced0fb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000ced0fc00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff0000ced0fc80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff0000ced0fd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff0000ced0fd80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb

Fixes: ab7ac4eb98 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot+b72d86aa5df17ce74c60@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b72d86aa5df17ce74c60
Tested-by: syzbot+b72d86aa5df17ce74c60@syzkaller.appspotmail.com
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20240815220437.69511-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2024-08-19 18:36:12 -07:00
arch KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX) 2024-08-14 12:28:24 -04:00
block blk-throttle: remove more latency dead-code 2024-07-27 10:33:25 -06:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation Including fixes from wireless and netfilter 2024-08-15 10:35:20 -07:00
drivers bluetooth pull request for net: 2024-08-16 19:07:31 -07:00
fs for-6.11-rc3-tag 2024-08-14 17:56:15 -07:00
include kcm: Serialise kcm_sendmsg() for the same socket. 2024-08-19 18:36:12 -07:00
init rust: SHADOW_CALL_STACK is incompatible with Rust 2024-08-01 16:15:03 +01:00
io_uring io_uring/net: don't pick multiple buffers for non-bundle send 2024-08-07 15:20:52 -06:00
ipc sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-24 20:59:29 +02:00
kernel vfs-6.11-rc4.fixes 2024-08-14 09:06:28 -07:00
lib minmax: don't use max() in situations that want a C constant expression 2024-07-28 20:23:27 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm 9 hotfixes. 5 are cc:stable, 4 either pertain to post-6.10 material or 2024-08-08 07:32:20 -07:00
net kcm: Serialise kcm_sendmsg() for the same socket. 2024-08-19 18:36:12 -07:00
rust rust: firmware: fix invalid rustdoc link 2024-07-31 13:24:29 +02:00
samples Driver core changes for 6.11-rc1 2024-07-25 10:42:22 -07:00
scripts syscalls: add back legacy __NR_nfsservctl macro 2024-08-06 08:57:02 +02:00
security selinux: revert our use of vma_is_initial_heap() 2024-08-08 16:22:47 -04:00
sound ASoC: Fixes for v6.11 2024-08-09 09:58:07 +02:00
tools selftests: udpgro: no need to load xdp for gro 2024-08-19 09:54:24 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX) 2024-08-14 12:28:24 -04:00
.clang-format Docs: Move clang-format from process/ to dev-tools/ 2024-06-26 16:36:00 -06:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.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: add script and target to generate pacman package 2024-07-22 01:24:22 +09:00
.mailmap mailmap: update entry for David Heidelberg 2024-08-07 18:33:56 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS tracing: Update of MAINTAINERS and CREDITS file 2024-07-18 14:08:42 -07:00
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 MAINTAINERS: add selftests to network drivers 2024-08-15 19:13:12 -07:00
Makefile Linux 6.11-rc3 2024-08-11 14:27:14 -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.