* [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6)
@ 2025-11-02 21:10 syzbot
2025-11-18 8:00 ` syzbot
0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2025-11-02 21:10 UTC (permalink / raw)
To: deller, dri-devel, linux-fbdev, linux-kernel, simona, soci,
syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 691d401c7e0e Merge tag 'spi-fix-v6.18-rc3' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14607932580000
kernel config: https://syzkaller.appspot.com/x/.config?x=19d831c6d0386a9c
dashboard link: https://syzkaller.appspot.com/bug?extid=5a40432dfe8f86ee657a
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5eaccda03e4f/disk-691d401c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0df5294a69bc/vmlinux-691d401c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f4f242731772/bzImage-691d401c.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5a40432dfe8f86ee657a@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline]
BUG: KASAN: vmalloc-out-of-bounds in fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1a6f/0x1e60 drivers/video/fbdev/core/sysimgblt.c:24
Write of size 8 at addr ffffc90003e99280 by task kworker/0:2/781
CPU: 0 UID: 0 PID: 781 Comm: kworker/0:2 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_power_efficient fb_flashcursor
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline]
fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline]
fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline]
fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline]
sys_imageblit+0x1a6f/0x1e60 drivers/video/fbdev/core/sysimgblt.c:24
drm_fbdev_shmem_defio_imageblit+0x20/0x130 drivers/gpu/drm/drm_fbdev_shmem.c:38
soft_cursor+0x524/0xa10 drivers/video/fbdev/core/softcursor.c:74
bit_cursor+0xe8c/0x17e0 drivers/video/fbdev/core/bitblit.c:395
fb_flashcursor drivers/video/fbdev/core/fbcon.c:401 [inline]
fb_flashcursor+0x310/0x400 drivers/video/fbdev/core/fbcon.c:370
process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
process_scheduled_works kernel/workqueue.c:3346 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
ffffc90003e99180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90003e99200: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90003e99280: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^
ffffc90003e99300: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90003e99380: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================
---
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^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6) 2025-11-02 21:10 [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6) syzbot @ 2025-11-18 8:00 ` syzbot 2025-11-19 10:18 ` shaurya 0 siblings, 1 reply; 4+ messages in thread From: syzbot @ 2025-11-18 8:00 UTC (permalink / raw) To: deller, dri-devel, linux-fbdev, linux-kernel, simona, soci, syzkaller-bugs syzbot has found a reproducer for the following issue on: HEAD commit: e7c375b18160 Merge tag 'vfs-6.18-rc7.fixes' of gitolite.ke.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15476692580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f dashboard link: https://syzkaller.appspot.com/bug?extid=5a40432dfe8f86ee657a compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10a70332580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173228b4580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/1fcb660703f1/disk-e7c375b1.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/4bf314965321/vmlinux-e7c375b1.xz kernel image: https://storage.googleapis.com/syzbot-assets/456b373fea36/bzImage-e7c375b1.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+5a40432dfe8f86ee657a@syzkaller.appspotmail.com RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fff34de03f0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fd0417e5fa0 R14: 00007fd0417e5fa0 R15: 0000000000000003 </TASK> ================================================================== BUG: KASAN: vmalloc-out-of-bounds in fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline] BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline] BUG: KASAN: vmalloc-out-of-bounds in fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline] BUG: KASAN: vmalloc-out-of-bounds in fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline] BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1a6f/0x1e60 drivers/video/fbdev/core/sysimgblt.c:24 Write of size 8 at addr ffffc90003749fc0 by task syz.0.17/6037 CPU: 0 UID: 0 PID: 6037 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xcd/0x630 mm/kasan/report.c:482 kasan_report+0xe0/0x110 mm/kasan/report.c:595 fb_write_offset drivers/video/fbdev/core/sysmem.h:30 [inline] fb_bitmap_2ppw drivers/video/fbdev/core/fb_imageblit.h:364 [inline] fb_bitmap_imageblit drivers/video/fbdev/core/fb_imageblit.h:462 [inline] fb_imageblit drivers/video/fbdev/core/fb_imageblit.h:492 [inline] sys_imageblit+0x1a6f/0x1e60 drivers/video/fbdev/core/sysimgblt.c:24 drm_fbdev_shmem_defio_imageblit+0x20/0x130 drivers/gpu/drm/drm_fbdev_shmem.c:38 cw_putcs_aligned drivers/video/fbdev/core/fbcon_cw.c:110 [inline] cw_putcs+0x917/0xbb0 drivers/video/fbdev/core/fbcon_cw.c:158 fbcon_putcs+0x387/0x450 drivers/video/fbdev/core/fbcon.c:1320 do_update_region+0x2e9/0x3f0 drivers/tty/vt/vt.c:628 redraw_screen+0x63f/0x760 drivers/tty/vt/vt.c:980 fbcon_modechanged+0x456/0x6b0 drivers/video/fbdev/core/fbcon.c:2710 fbcon_rotate drivers/video/fbdev/core/fbcon.c:228 [inline] rotate_store+0x258/0x2f0 drivers/video/fbdev/core/fbcon.c:3215 dev_attr_store+0x58/0x80 drivers/base/core.c:2437 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd04158f6c9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff34de0398 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fd0417e5fa0 RCX: 00007fd04158f6c9 RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007fff34de03f0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fd0417e5fa0 R14: 00007fd0417e5fa0 R15: 0000000000000003 </TASK> The buggy address belongs to a vmalloc virtual mapping Memory state around the buggy address: ffffc90003749e80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90003749f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >ffffc90003749f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ ffffc9000374a000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc9000374a080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6) 2025-11-18 8:00 ` syzbot @ 2025-11-19 10:18 ` shaurya 2025-11-19 10:42 ` syzbot 0 siblings, 1 reply; 4+ messages in thread From: shaurya @ 2025-11-19 10:18 UTC (permalink / raw) To: syzbot+5a40432dfe8f86ee657a; +Cc: linux-fbdev, linux-kernel, syzkaller-bugs [-- Attachment #1: Type: text/plain, Size: 82 bytes --] #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master [-- Attachment #2: 0001-testing-my-fix.patch --] [-- Type: text/x-patch, Size: 3132 bytes --] From 188fc7eea4a00500a806b7b122d20289abc2bf00 Mon Sep 17 00:00:00 2001 From: Shaurya Rane <ssrane_b23@ee.vjti.ac.in> Date: Wed, 19 Nov 2025 15:44:51 +0530 Subject: [PATCH] testing my fix Signed-off-by: Shaurya Rane <ssrane_b23@ee.vjti.ac.in> --- drivers/video/fbdev/core/fb_imageblit.h | 66 +++++++++++++++++++++++-- 1 file changed, 62 insertions(+), 4 deletions(-) diff --git a/drivers/video/fbdev/core/fb_imageblit.h b/drivers/video/fbdev/core/fb_imageblit.h index 3b2bb4946505..aee7f4032164 100644 --- a/drivers/video/fbdev/core/fb_imageblit.h +++ b/drivers/video/fbdev/core/fb_imageblit.h @@ -485,11 +485,69 @@ static inline void fb_imageblit(struct fb_info *p, const struct fb_image *image) struct fb_address dst = fb_address_init(p); struct fb_reverse reverse = fb_reverse_init(p); const u32 *palette = fb_palette(p); + struct fb_image clipped_image; + u32 max_x, max_y; + unsigned long max_offset_bytes; + + /* Validate basic parameters */ + if (!image || !p->screen_buffer || !p->screen_size || + !image->width || !image->height) + return; + + /* Calculate maximum addressable coordinates based on virtual resolution and buffer size */ + max_x = p->var.xres_virtual; + max_y = p->var.yres_virtual; + + /* Also check against actual buffer size to prevent vmalloc overflow */ + { + unsigned long effective_width_bytes; + u32 right_edge = image->dx + image->width; + + if (right_edge < image->dx) + right_edge = max_x; + else + right_edge = min(right_edge, max_x); + + effective_width_bytes = (unsigned long)right_edge * bpp; + effective_width_bytes = (effective_width_bytes + 7) / 8; + + if (effective_width_bytes > p->screen_size) { + max_y = 0; + } else if (p->fix.line_length) { + u32 max_lines = (p->screen_size - effective_width_bytes) / + p->fix.line_length + 1; + if (max_lines < max_y) + max_y = max_lines; + } + } + + /* If image is completely outside bounds, skip it */ + if (image->dx >= max_x || image->dy >= max_y) + return; + + /* Create clipped image - clip to virtual resolution bounds */ + clipped_image = *image; + + /* Clip width if it extends beyond right edge */ + if (clipped_image.dx + clipped_image.width > max_x) { + if (clipped_image.dx < max_x) + clipped_image.width = max_x - clipped_image.dx; + else + return; /* completely outside */ + } + + /* Clip height if it extends beyond bottom edge */ + if (clipped_image.dy + clipped_image.height > max_y) { + if (clipped_image.dy < max_y) + clipped_image.height = max_y - clipped_image.dy; + else + return; /* completely outside */ + } - fb_address_forward(&dst, image->dy * bits_per_line + image->dx * bpp); + fb_address_forward(&dst, clipped_image.dy * bits_per_line + clipped_image.dx * bpp); - if (image->depth == 1) - fb_bitmap_imageblit(image, &dst, bits_per_line, palette, bpp, reverse); + if (clipped_image.depth == 1) + fb_bitmap_imageblit(&clipped_image, &dst, bits_per_line, palette, bpp, reverse); else - fb_color_imageblit(image, &dst, bits_per_line, palette, bpp, reverse); + fb_color_imageblit(&clipped_image, &dst, bits_per_line, palette, bpp, reverse); } -- 2.34.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6) 2025-11-19 10:18 ` shaurya @ 2025-11-19 10:42 ` syzbot 0 siblings, 0 replies; 4+ messages in thread From: syzbot @ 2025-11-19 10:42 UTC (permalink / raw) To: linux-fbdev, linux-kernel, ssranevjti, syzkaller-bugs Hello, syzbot has tested the proposed patch and the reproducer did not trigger any issue: Reported-by: syzbot+5a40432dfe8f86ee657a@syzkaller.appspotmail.com Tested-by: syzbot+5a40432dfe8f86ee657a@syzkaller.appspotmail.com Tested on: commit: 8b690556 Merge tag 'for-linus' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10921212580000 kernel config: https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f dashboard link: https://syzkaller.appspot.com/bug?extid=5a40432dfe8f86ee657a compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=13a21212580000 Note: testing is done by a robot and is best-effort only. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-11-19 10:42 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2025-11-02 21:10 [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (6) syzbot 2025-11-18 8:00 ` syzbot 2025-11-19 10:18 ` shaurya 2025-11-19 10:42 ` syzbot
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