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Quanmin Yan de89d19f4f fbcon: Set fb_display[i]->mode to NULL when the mode is released 
commit a1f3058930 upstream.

Recently, we discovered the following issue through syzkaller:

BUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0
Read of size 4 at addr ff11000001b3c69c by task syz.xxx
...
Call Trace:
 <TASK>
 dump_stack_lvl+0xab/0xe0
 print_address_description.constprop.0+0x2c/0x390
 print_report+0xb9/0x280
 kasan_report+0xb8/0xf0
 fb_mode_is_equal+0x285/0x2f0
 fbcon_mode_deleted+0x129/0x180
 fb_set_var+0xe7f/0x11d0
 do_fb_ioctl+0x6a0/0x750
 fb_ioctl+0xe0/0x140
 __x64_sys_ioctl+0x193/0x210
 do_syscall_64+0x5f/0x9c0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Based on experimentation and analysis, during framebuffer unregistration,
only the memory of fb_info->modelist is freed, without setting the
corresponding fb_display[i]->mode to NULL for the freed modes. This leads
to UAF issues during subsequent accesses. Here's an example of reproduction
steps:
1. With /dev/fb0 already registered in the system, load a kernel module
   to register a new device /dev/fb1;
2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP);
3. Switch console from fb to VGA (to allow normal rmmod of the ko);
4. Unload the kernel module, at this point fb1's modelist is freed, leaving
   a wild pointer in fb_display[];
5. Trigger the bug via system calls through fb0 attempting to delete a mode
   from fb0.

Add a check in do_unregister_framebuffer(): if the mode to be freed exists
in fb_display[], set the corresponding mode pointer to NULL.

Signed-off-by: Quanmin Yan <yanquanmin1@huawei.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-11-13 15:36:36 -05:00
arch arch: Add the macro COMPILE_OFFSETS to all the asm-offsets.c 2025-11-02 22:18:04 +09:00
block block: require LBA dma_alignment when using PI 2025-10-29 14:10:28 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:37:14 +02:00
Documentation x86/bugs: Add attack vector controls for VMSCAPE 2025-11-02 22:18:03 +09:00
drivers fbcon: Set fb_display[i]->mode to NULL when the mode is released 2025-11-13 15:36:36 -05:00
fs Revert "NFSD: Remove the cap on number of operations per NFSv4 COMPOUND" 2025-11-13 15:36:36 -05:00
include fbcon: Set fb_display[i]->mode to NULL when the mode is released 2025-11-13 15:36:36 -05:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:37:27 +02:00
io_uring io_uring: correct __must_hold annotation in io_install_fixed_file 2025-10-29 14:10:28 +01:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel sched_ext: Mark scx_bpf_dsq_move_set_[slice|vtime]() with KF_RCU 2025-11-13 15:36:36 -05:00
lib lib/genalloc: fix device leak in of_gen_pool_get() 2025-10-19 16:37:28 +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 treewide: remove MIGRATEPAGE_SUCCESS 2025-10-29 14:10:32 +01:00
net Revert "Bluetooth: L2CAP: convert timeouts to secs_to_jiffies()" 2025-11-13 15:36:36 -05:00
rust rust: device: fix device context of Device::parent() 2025-10-29 14:10:22 +01:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts kbuild: Add '.rel.*' strip pattern for vmlinux 2025-10-19 16:37:15 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:37:28 +02:00
sound ASoC: amd/sdw_utils: avoid NULL deref when devm_kasprintf() fails 2025-10-23 16:24:37 +02:00
tools sched_ext: Make qmap dump operation non-destructive 2025-11-02 22:18:04 +09:00
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 6.17.7 2025-11-02 22:18:05 +09:00
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.