On 11/12/25 08:32, Gu Bowen wrote:
There was an out-of-bounds issue found by syzkaller test on v6.6.
BUG: unable to handle page fault for address: ffffc90000c3f000
PGD 100000067 P4D 100000067 PUD 100c80067 PMD 10ac1c067 PTE 0
Oops: 0002 [#1] PREEMPT SMP KASAN PTI
CPU: 3 PID: 6521 Comm: syz.3.1365 Not tainted 6.6.0+ #82
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
RIP: 0010:memset64 arch/x86/include/asm/string_64.h:58 [inline]
RIP: 0010:memset_l include/linux/string.h:168 [inline]
RIP: 0010:bitfill_aligned drivers/video/fbdev/core/sysfillrect.c:53 [inline]
RIP: 0010:bitfill_aligned+0x144/0x1c0 drivers/video/fbdev/core/sysfillrect.c:25
Code: 23 04 24 48 31 d0 49 89 46 f8 44 89 e0 44 29 f8 29 c3 e8 9f 39 49 fe 89 d8 31
d2 4c 89 f7 41 f7 f4 48 89 c3 48 89 c1 48 89 e8 <f3> 48 ab 31 ff 4c 89 ee e8 df
2f 49 fe 4d 85 ed 0f 84 6b ff ff ff
RSP: 0018:ffff888119ce7418 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000180 RCX: 0000000000000180
RDX: 0000000000000000 RSI: ffffc90003873000 RDI: ffffc90000c3f000
RBP: 0000000000000000 R08: 0000000000006000 R09: 0000000000000040
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000040
R13: 0000000000000000 R14: ffffc90000c3f000 R15: 0000000000000000
FS: 00007f1704b926c0(0000) GS:ffff8881f5980000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc90000c3f000 CR3: 00000001230d0002 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 000000000000e000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
PKRU: 80000000
Call Trace:
<TASK>
sys_fillrect+0x429/0x830 drivers/video/fbdev/core/sysfillrect.c:281
drm_fbdev_generic_defio_fillrect+0x27/0x140
drivers/gpu/drm/drm_fbdev_generic.c:37
bit_clear+0x183/0x220 drivers/video/fbdev/core/bitblit.c:73
__fbcon_clear+0x5ea/0x670 drivers/video/fbdev/core/fbcon.c:1281
fbcon_scroll+0x41e/0x560 drivers/video/fbdev/core/fbcon.c:1847
con_scroll+0x464/0x6a0 drivers/tty/vt/vt.c:577
lf+0x274/0x2d0 drivers/tty/vt/vt.c:1461
do_con_trol+0x5ea/0x3d80 drivers/tty/vt/vt.c:2149
do_con_write+0x780/0x10c0 drivers/tty/vt/vt.c:2905
con_write+0x28/0xc0 drivers/tty/vt/vt.c:3245
do_output_char+0x5de/0x850 drivers/tty/n_tty.c:433
process_output drivers/tty/n_tty.c:500 [inline]
n_tty_write+0x442/0xb00 drivers/tty/n_tty.c:2406
iterate_tty_write+0x2b5/0x630 drivers/tty/tty_io.c:1017
file_tty_write.constprop.0+0x20c/0x3b0 drivers/tty/tty_io.c:1088
call_write_iter include/linux/fs.h:2085 [inline]
do_iter_readv_writev+0x210/0x3c0 fs/read_write.c:737
do_iter_write+0x181/0x4e0 fs/read_write.c:862
vfs_writev+0x15b/0x4d0 fs/read_write.c:935
do_writev+0x136/0x370 fs/read_write.c:978
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
When the virtual console is rotated in the backend state, it can lead to
inconsistencies between the size of the virtual console's size and its
hook functions. In such cases, clearing the screen may result in
out-of-bounds issue.
Fix it by adding a check in sys_fillrect() and moving set_blitting_type()
to the visible area of the VC.
CC: [email protected] # fbdev had been refactored on 6.15-rc1
Fixes: 68648ed1f58d ("fbdev: add drawing functions for framebuffers in system
RAM")
Signed-off-by: Gu Bowen <[email protected]>
---
drivers/video/fbdev/core/fbcon.c | 2 +-
drivers/video/fbdev/core/sysfillrect.c | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)
That patch does not apply to git head.
Can you try to reproduce with git head?
Helge
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index b49f15a3442e..a6602f230089 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -2702,9 +2702,9 @@ static void fbcon_modechanged(struct fb_info *info)
return;
p = &fb_display[vc->vc_num];
- set_blitting_type(vc, info);
if (con_is_visible(vc)) {
+ set_blitting_type(vc, info);
var_to_display(p, &info->var, info);
cols = FBCON_SWAP(ops->rotate, info->var.xres, info->var.yres);
rows = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres);
diff --git a/drivers/video/fbdev/core/sysfillrect.c
b/drivers/video/fbdev/core/sysfillrect.c
index bcdcaeae6538..e5c4ee317b0b 100644
--- a/drivers/video/fbdev/core/sysfillrect.c
+++ b/drivers/video/fbdev/core/sysfillrect.c
@@ -238,6 +238,7 @@ void sys_fillrect(struct fb_info *p, const struct
fb_fillrect *rect)
u32 bpp = p->var.bits_per_pixel;
unsigned long *dst;
int dst_idx, left;
+ long dst_offset;
if (p->state != FBINFO_STATE_RUNNING)
return;
@@ -277,6 +278,11 @@ void sys_fillrect(struct fb_info *p, const struct
fb_fillrect *rect)
}
while (height--) {
dst += dst_idx >> (ffs(bits) - 1);
+ dst_offset = (unsigned long)dst - (unsigned
long)p->screen_base;
+ if (dst_offset < 0 || dst_offset >= p->fix.smem_len) {
+ pr_err("dst offset out of bound:
dst_offset(%ld)", dst_offset);
+ return;
+ }
dst_idx &= (bits - 1);
fill_op32(p, dst, dst_idx, pat, width*bpp, bits);
dst_idx += p->fix.line_length*8;
