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Date: Sun, 10 Oct 2021 06:42:28 +0000
From: Zheyu Ma <zheyuma97@...il.com>
To: dri-devel@...ts.freedesktop.org
Cc: linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
Zheyu Ma <zheyuma97@...il.com>
Subject: [PATCH 2/2] fbdev: fbmem: Fix double free of 'fb_info->pixmap.addr'
savagefb and some other drivers call kfree to free 'info->pixmap.addr'
even after calling unregister_framebuffer, which may cause double free.
Fix this by setting 'fb_info->pixmap.addr' to NULL after kfree in
unregister_framebuffer.
The following log reveals it:
[ 37.318872] BUG: KASAN: double-free or invalid-free in kfree+0x13e/0x290
[ 37.319369]
[ 37.320803] Call Trace:
[ 37.320992] dump_stack_lvl+0xa8/0xd1
[ 37.321274] print_address_description+0x87/0x3b0
[ 37.321632] ? kfree+0x13e/0x290
[ 37.321879] ? kfree+0x13e/0x290
[ 37.322126] ? kfree+0x13e/0x290
[ 37.322374] kasan_report_invalid_free+0x58/0x90
[ 37.322724] ____kasan_slab_free+0x123/0x140
[ 37.323049] __kasan_slab_free+0x11/0x20
[ 37.323347] slab_free_freelist_hook+0x81/0x150
[ 37.323689] ? savagefb_remove+0xa1/0xc0 [savagefb]
[ 37.324066] kfree+0x13e/0x290
[ 37.324304] savagefb_remove+0xa1/0xc0 [savagefb]
[ 37.324655] pci_device_remove+0xa9/0x250
[ 37.324959] ? pci_device_probe+0x7d0/0x7d0
[ 37.325273] device_release_driver_internal+0x4f7/0x7a0
[ 37.325666] driver_detach+0x1e8/0x2c0
[ 37.325952] bus_remove_driver+0x134/0x290
[ 37.326262] ? sysfs_remove_groups+0x97/0xb0
[ 37.326584] driver_unregister+0x77/0xa0
[ 37.326883] pci_unregister_driver+0x2c/0x1c0
[ 37.336124]
[ 37.336245] Allocated by task 5465:
[ 37.336507] ____kasan_kmalloc+0xb5/0xe0
[ 37.336801] __kasan_kmalloc+0x9/0x10
[ 37.337069] kmem_cache_alloc_trace+0x12b/0x220
[ 37.337405] register_framebuffer+0x3f3/0xa00
[ 37.337731] foo_register_framebuffer+0x3b/0x50 [savagefb]
[ 37.338136]
[ 37.338255] Freed by task 5475:
[ 37.338492] kasan_set_track+0x3d/0x70
[ 37.338774] kasan_set_free_info+0x23/0x40
[ 37.339081] ____kasan_slab_free+0x10b/0x140
[ 37.339399] __kasan_slab_free+0x11/0x20
[ 37.339694] slab_free_freelist_hook+0x81/0x150
[ 37.340034] kfree+0x13e/0x290
[ 37.340267] do_unregister_framebuffer+0x21c/0x3d0
[ 37.340624] unregister_framebuffer+0x23/0x40
[ 37.340950] savagefb_remove+0x45/0xc0 [savagefb]
[ 37.341302] pci_device_remove+0xa9/0x250
[ 37.341603] device_release_driver_internal+0x4f7/0x7a0
[ 37.341990] driver_detach+0x1e8/0x2c0
[ 37.342272] bus_remove_driver+0x134/0x290
[ 37.342577] driver_unregister+0x77/0xa0
[ 37.342873] pci_unregister_driver+0x2c/0x1c0
[ 37.343196] cleanup_module+0x15/0x1c [savagefb]
[ 37.343543] __se_sys_delete_module+0x398/0x490
[ 37.343881] __x64_sys_delete_module+0x56/0x60
[ 37.344221] do_syscall_64+0x4d/0xc0
[ 37.344492] entry_SYSCALL_64_after_hwframe+0x44/0xae
Signed-off-by: Zheyu Ma <zheyuma97@...il.com>
---
drivers/video/fbdev/core/fbmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 7420d2c16e47..b81b0e37daed 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -1702,8 +1702,10 @@ static void do_unregister_framebuffer(struct fb_info *fb_info)
{
unlink_framebuffer(fb_info);
if (fb_info->pixmap.addr &&
- (fb_info->pixmap.flags & FB_PIXMAP_DEFAULT))
+ (fb_info->pixmap.flags & FB_PIXMAP_DEFAULT)) {
kfree(fb_info->pixmap.addr);
+ fb_info->pixmap.addr = NULL;
+ }
fb_destroy_modelist(&fb_info->modelist);
registered_fb[fb_info->node] = NULL;
num_registered_fb--;
--
2.17.6
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