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Anderson Nascimento 73ce2a774a fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing 
[ Upstream commit 62e59ffe87 ]

The function do_fanotify_mark() does not validate if
mnt_ns_from_dentry() returns NULL before dereferencing mntns->user_ns.
This causes a NULL pointer dereference in do_fanotify_mark() if the
path is not a mount namespace object.

Fix this by checking mnt_ns_from_dentry()'s return value before
dereferencing it.

Before the patch

$ gcc fanotify_nullptr.c -o fanotify_nullptr
$ mkdir A
$ ./fanotify_nullptr
Fanotify fd: 3
fanotify_mark: Operation not permitted
$ unshare -Urm
Fanotify fd: 3
Killed

int main(void){
    int ffd;
    ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0);
    if(ffd < 0){
        perror("fanotify_init");
        exit(EXIT_FAILURE);
    }

    printf("Fanotify fd: %d\n",ffd);

    if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS,
FAN_MNT_ATTACH, AT_FDCWD, "A") < 0){
        perror("fanotify_mark");
        exit(EXIT_FAILURE);
    }

return 0;
}

After the patch

$ gcc fanotify_nullptr.c -o fanotify_nullptr
$ mkdir A
$ ./fanotify_nullptr
Fanotify fd: 3
fanotify_mark: Operation not permitted
$ unshare -Urm
Fanotify fd: 3
fanotify_mark: Invalid argument

[   25.694973] BUG: kernel NULL pointer dereference, address: 0000000000000038
[   25.695006] #PF: supervisor read access in kernel mode
[   25.695012] #PF: error_code(0x0000) - not-present page
[   25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0
[   25.695025] Oops: Oops: 0000 [#1] SMP NOPTI
[   25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt Not
tainted 6.17.0-rc4 #1 PREEMPT(lazy)
[   25.695040] Hardware name: VMware, Inc. VMware Virtual
Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
[   25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950
[   25.695066] Code: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54
24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b
5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28
85 c9
[   25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203
[   25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220
[   25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180
[   25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000
[   25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7
[   25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0
[   25.695154] FS:  00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000)
knlGS:0000000000000000
[   25.695162] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0
[   25.695201] Call Trace:
[   25.695209]  <TASK>
[   25.695215]  __x64_sys_fanotify_mark+0x1f/0x30
[   25.695222]  do_syscall_64+0x82/0x2c0
...

Fixes: 58f5fbeb36 ("fanotify: support watching filesystems and mounts inside userns")
Link: https://patch.msgid.link/CAPhRvkw4ONypNsJrCnxbKnJbYmLHTDEKFC4C_num_5sVBVa8jg@mail.gmail.com
Signed-off-by: Anderson Nascimento <anderson@allelesecurity.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-15 12:03:52 +02:00
arch arm64: dts: apple: Add ethernet0 alias for J375 template 2025-10-15 12:03:35 +02:00
block blk-throttle: fix throtl_data leak during disk release 2025-10-15 12:03:34 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: rng - Ensure set_ent is always present 2025-10-12 13:01:57 +02:00
Documentation docs: iio: ad3552r: Fix malformed code-block directive 2025-10-15 12:03:43 +02:00
drivers PCI: qcom: Add equalization settings for 8.0 GT/s and 32.0 GT/s 2025-10-15 12:03:52 +02:00
fs fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing 2025-10-15 12:03:52 +02:00
include wifi: brcmfmac: fix 43752 SDIO FWVID incorrectly labelled as Cypress (CYW) 2025-10-15 12:03:52 +02:00
init Fix CC_HAS_ASM_GOTO_OUTPUT on non-x86 architectures 2025-10-15 12:03:13 +02:00
io_uring io_uring-6.17-20250919 2025-09-19 12:10:49 -07:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel bpf: Enforce expected_attach_type for tailcall compatibility 2025-10-15 12:03:39 +02:00
lib vdso/datastore: Gate time data behind CONFIG_GENERIC_GETTIMEOFDAY 2025-10-15 12:03:24 +02:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mptcp: Fix up subflow's memcg when CONFIG_SOCK_CGROUP_DATA=n. 2025-10-15 12:03:44 +02:00
net tcp: fix __tcp_close() to only send RST when required 2025-10-15 12:03:52 +02:00
rust rust: cpumask: Mark CpumaskVar as transparent 2025-10-15 12:03:19 +02:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts scripts/misc-check: update export checks for EXPORT_SYMBOL_FOR_MODULES() 2025-10-15 12:03:22 +02:00
security lsm: CONFIG_LSM can depend on CONFIG_SECURITY 2025-10-15 12:03:17 +02:00
sound ALSA: lx_core: use int type to store negative error codes 2025-10-15 12:03:47 +02:00
tools libbpf: Fix error when st-prefix_ops and ops from differ btf 2025-10-15 12:03:38 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap 7 hotfixes. 4 are cc:stable and the remainder address post-6.16 issues or 2025-09-28 09:32:00 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.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: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS i2c-for-6.17-rc8 2025-09-28 13:19:23 -07:00
Makefile Linux 6.17.2 2025-10-12 13:01:58 +02:00
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.