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Jiayuan Chen 1c8bda3df0 net: atm: fix crash due to unvalidated vcc pointer in sigd_send() 
[ Upstream commit ae88a5d2f2 ]

Reproducer available at [1].

The ATM send path (sendmsg -> vcc_sendmsg -> sigd_send) reads the vcc
pointer from msg->vcc and uses it directly without any validation. This
pointer comes from userspace via sendmsg() and can be arbitrarily forged:

    int fd = socket(AF_ATMSVC, SOCK_DGRAM, 0);
    ioctl(fd, ATMSIGD_CTRL);  // become ATM signaling daemon
    struct msghdr msg = { .msg_iov = &iov, ... };
    *(unsigned long *)(buf + 4) = 0xdeadbeef;  // fake vcc pointer
    sendmsg(fd, &msg, 0);  // kernel dereferences 0xdeadbeef

In normal operation, the kernel sends the vcc pointer to the signaling
daemon via sigd_enq() when processing operations like connect(), bind(),
or listen(). The daemon is expected to return the same pointer when
responding. However, a malicious daemon can send arbitrary pointer values.

Fix this by introducing find_get_vcc() which validates the pointer by
searching through vcc_hash (similar to how sigd_close() iterates over
all VCCs), and acquires a reference via sock_hold() if found.

Since struct atm_vcc embeds struct sock as its first member, they share
the same lifetime. Therefore using sock_hold/sock_put is sufficient to
keep the vcc alive while it is being used.

Note that there may be a race with sigd_close() which could mark the vcc
with various flags (e.g., ATM_VF_RELEASED) after find_get_vcc() returns.
However, sock_hold() guarantees the memory remains valid, so this race
only affects the logical state, not memory safety.

[1]: https://gist.github.com/mrpre/1ba5949c45529c511152e2f4c755b0f3
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: syzbot+1f22cb1769f249df9fa0@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69039850.a70a0220.5b2ed.005d.GAE@google.com/T/
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Link: https://patch.msgid.link/20260205095501.131890-1-jiayuan.chen@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:19:38 -05:00
arch arm64: dts: qcom: sdm845-db845c: specify power for WiFi CH1 2026-03-04 07:19:30 -05:00
block block,bfq: fix aux stat accumulation destination 2026-02-11 13:35:29 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-02-06 16:41:53 +01:00
Documentation PCI: endpoint: Automatically create a function specific attributes group 2026-02-19 16:21:46 +01:00
drivers net: hns3: fix double free issue for tx spare buffer 2026-03-04 07:19:37 -05:00
fs procfs: fix missing RCU protection when reading real_parent in do_task_stat() 2026-03-04 07:19:37 -05:00
include ethtool: add support to set/get tx copybreak buf size via ethtool 2026-03-04 07:19:36 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring: fix filename leak in __io_openat_prep() 2026-01-19 13:09:54 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel timers: Replace in_irq() with in_hardirq() 2026-03-04 07:19:36 -05:00
lib lib/crypto: aes: Fix missing MMU protection for AES S-box 2026-01-19 13:10:13 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/kfence: randomize the freelist on initialization 2026-02-11 13:35:27 +01:00
net net: atm: fix crash due to unvalidated vcc pointer in sigd_send() 2026-03-04 07:19:38 -05:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts kbuild: Use CRC32 and a 1MiB dictionary for XZ compressed modules 2026-01-19 13:10:05 +01:00
security smack: /smack/doi: accept previously used values 2026-03-04 07:19:31 -05:00
sound ASoC: fsl_xcvr: fix missing lock in fsl_xcvr_mode_put() 2026-02-19 16:21:44 +01:00
tools spi: tools: Add include folder to .gitignore 2026-03-04 07:19:32 -05:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:35:27 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.201 2026-02-19 16:21:47 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 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.