[syzbot] [fbdev?] KASAN: global-out-of-bounds Read in bit_putcs (3)

syzbot
2024-07-31T11:38:20Z

Hello,

syzbot found the following issue on:

HEAD commit: c912bf709078 Merge remote-tracking branches 'origin/arm64-..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=13b495bd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=35545feca25ede03
dashboard link: https://syzkaller.appspot.com/bug?extid=793cf822d213be1a74f2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/caeac6485006/disk-c912bf70.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/501c87f28da9/vmlinux-c912bf70.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6812e99b7182/Image-c912bf70.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:633 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs+0x9b8/0xe30 drivers/video/fbdev/core/bitblit.c:185
Read of size 1 at addr ffff80008b830d80 by task syz.1.1270/10828

CPU: 0 PID: 10828 Comm: syz.1.1270 Not tainted 6.10.0-rc7-syzkaller-gc912bf709078 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x198/0x538 mm/kasan/report.c:488
kasan_report+0xd8/0x138 mm/kasan/report.c:601
__asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378
__fb_pad_aligned_buffer include/linux/fb.h:633 [inline]
bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
bit_putcs+0x9b8/0xe30 drivers/video/fbdev/core/bitblit.c:185
fbcon_putcs+0x318/0x4e8 drivers/video/fbdev/core/fbcon.c:1288
do_update_region+0x1e8/0x3d0 drivers/tty/vt/vt.c:609
update_region+0x1e0/0x478 drivers/tty/vt/vt.c:633
vcs_write+0x90c/0x10c8 drivers/tty/vt/vc_screen.c:698
do_loop_readv_writev fs/read_write.c:764 [inline]
vfs_writev+0x5c8/0xb80 fs/read_write.c:973
do_writev+0x178/0x304 fs/read_write.c:1018
__do_sys_writev fs/read_write.c:1091 [inline]
__se_sys_writev fs/read_write.c:1088 [inline]
__arm64_sys_writev+0x80/0x94 fs/read_write.c:1088
__invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:48
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:131
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:150
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

The buggy address belongs to the variable:
oid_data+0x340/0x3a0

The buggy address belongs to the virtual mapping at
[ffff80008b260000, ffff80008ee20000) created by:
declare_kernel_vmas+0x58/0xb8 arch/arm64/mm/mmu.c:770

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1a9430
flags: 0x5ffc00000002000(reserved|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000002000 fffffdffc5a50c08 fffffdffc5a50c08 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff80008b830c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff80008b830d00: 00 00 00 07 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>ffff80008b830d80: f9 f9 f9 f9 f9 f9 f9 f9 00 00 00 00 06 f9 f9 f9
^
ffff80008b830e00: 05 f9 f9 f9 06 f9 f9 f9 00 00 00 00 00 00 00 00
ffff80008b830e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 02 f9 f9
==================================================================

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