From 0c9cb9321cb3863b52bdea4b8ae5a27705762c9e Mon Sep 17 00:00:00 2001 From: Andrey Misiurov Date: Mon, 12 Oct 2026 19:53:38 +0200 Subject: [PATCH] fbdev: core: Initialize modelist in framebuffer_alloc() framebuffer_alloc() returns zeroed memory, so info->modelist starts out with NULL next and prev pointers. The list head is initialized only later, by fb_videomode_to_modelist() or by do_register_framebuffer(). The "fix potential memory leak" commits listed below added fb_destroy_modelist(&info->modelist) to the probe error paths of s3fb, tdfxfb, tridentfb, i740fb and carminefb. These paths can run before the list head is initialized: - s3fb, tdfxfb, tridentfb and i740fb call fb_videomode_to_modelist() only after a successful EDID read, and tridentfb can also hit the error path on an ioremap() or kmalloc() failure before that; - carminefb jumps to the error path when fb_find_mode() fails, before its fb_videomode_to_modelist() call. fb_destroy_modelist() then dereferences the NULL head. Reproduced on Debian 12 (6.1.180) by binding s3fb to a VGA device without EDID and forcing fb_alloc_cmap() to fail: s3fb 0000:00:03.0: cannot allocate colormap BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:fb_destroy_modelist+0x10/0x80 Call Trace: s3_pci_probe.cold+0x12b/0x2bf [s3fb] local_pci_probe+0x41/0x80 pci_device_probe+0xc3/0x240 really_probe+0xde/0x380 __driver_probe_device+0x84/0x150 driver_probe_device+0x1f/0x90 __driver_attach+0xce/0x1c0 bus_for_each_dev+0x87/0xd0 bus_add_driver+0x1ae/0x200 driver_register+0x89/0xe0 do_one_initcall+0x59/0x220 do_init_module+0x4a/0x1f0 Initialize the list head in framebuffer_alloc(), so info->modelist is always a valid, possibly empty, list and fb_destroy_modelist() is safe on every error path. Keep the lazy initialization in do_register_framebuffer(), as drivers that embed struct fb_info rather than calling framebuffer_alloc() still depend on it. Fixes: 3b0ed04bc852 ("fbdev: s3fb: fix potential memory leak in s3_pci_probe()") Fixes: bb019d755366 ("fbdev: tdfxfb: fix potential memory leak in tdfxfb_probe()") Fixes: 7a35ec619d9a ("fbdev: tridentfb: fix potential memory leak in trident_pci_probe()") Fixes: 5936063409af ("fbdev: i740fb: fix potential memory leak in i740fb_probe()") Fixes: 6fcca16a2b19 ("fbdev: carminefb: fix potential memory leak in alloc_carmine_fb()") Cc: stable@vger.kernel.org Signed-off-by: Andrey Misiurov Signed-off-by: Helge Deller --- drivers/video/fbdev/core/fb_info.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/video/fbdev/core/fb_info.c b/drivers/video/fbdev/core/fb_info.c index 52f9bd2c5417..05988a936beb 100644 --- a/drivers/video/fbdev/core/fb_info.c +++ b/drivers/video/fbdev/core/fb_info.c @@ -43,6 +43,7 @@ struct fb_info *framebuffer_alloc(size_t size, struct device *dev) info->device = dev; info->fbcon_rotate_hint = -1; info->blank = FB_BLANK_UNBLANK; + INIT_LIST_HEAD(&info->modelist); #if IS_ENABLED(CONFIG_FB_BACKLIGHT) mutex_init(&info->bl_curve_mutex);