kernel/linux.git/drivers/video/fbdev/core/fbcon.c, branch v6.6.131

fbcon: check return value of con2fb_acquire_newinfo()

2026-03-04T12:21:18+00:00

[ Upstream commit 011a0502801c8536f64141a2b61362c14f456544 ] If fbcon_open() fails when called from con2fb_acquire_newinfo() then info->fbcon_par pointer remains NULL which is later dereferenced. Add check for return value of the function con2fb_acquire_newinfo() to avoid it. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: d1baa4ffa677 ("fbcon: set_con2fb_map fixes") Cc: stable@vger.kernel.org Signed-off-by: Andrey Vatoropin Signed-off-by: Helge Deller Signed-off-by: Sasha Levin

fbcon: Set fb_display[i]->mode to NULL when the mode is released

2025-11-24T09:29:11+00:00

commit a1f3058930745d2b938b6b4f5bd9630dc74b26b7 upstream. Recently, we discovered the following issue through syzkaller: BUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0 Read of size 4 at addr ff11000001b3c69c by task syz.xxx ... Call Trace: dump_stack_lvl+0xab/0xe0 print_address_description.constprop.0+0x2c/0x390 print_report+0xb9/0x280 kasan_report+0xb8/0xf0 fb_mode_is_equal+0x285/0x2f0 fbcon_mode_deleted+0x129/0x180 fb_set_var+0xe7f/0x11d0 do_fb_ioctl+0x6a0/0x750 fb_ioctl+0xe0/0x140 __x64_sys_ioctl+0x193/0x210 do_syscall_64+0x5f/0x9c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Based on experimentation and analysis, during framebuffer unregistration, only the memory of fb_info->modelist is freed, without setting the corresponding fb_display[i]->mode to NULL for the freed modes. This leads to UAF issues during subsequent accesses. Here's an example of reproduction steps: 1. With /dev/fb0 already registered in the system, load a kernel module to register a new device /dev/fb1; 2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP); 3. Switch console from fb to VGA (to allow normal rmmod of the ko); 4. Unload the kernel module, at this point fb1's modelist is freed, leaving a wild pointer in fb_display[]; 5. Trigger the bug via system calls through fb0 attempting to delete a mode from fb0. Add a check in do_unregister_framebuffer(): if the mode to be freed exists in fb_display[], set the corresponding mode pointer to NULL. Signed-off-by: Quanmin Yan Reviewed-by: Thomas Zimmermann Signed-off-by: Helge Deller Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman

fbcon: Fix OOB access in font allocation

2025-10-02T11:42:54+00:00

commit 9b2f5ef00e852f8e8902a4d4f73aeedc60220c12 upstream. Commit 1a194e6c8e1e ("fbcon: fix integer overflow in fbcon_do_set_font") introduced an out-of-bounds access by storing data and allocation sizes in the same variable. Restore the old size calculation and use the new variable 'alloc_size' for the allocation. Signed-off-by: Thomas Zimmermann Fixes: 1a194e6c8e1e ("fbcon: fix integer overflow in fbcon_do_set_font") Reported-by: Jani Nikula Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15020 Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6201 Cc: Samasth Norway Ananda Cc: Thomas Zimmermann Cc: George Kennedy Cc: Greg Kroah-Hartman Cc: Simona Vetter Cc: Helge Deller Cc: "Ville Syrjälä" Cc: Sam Ravnborg Cc: Qianqiang Liu Cc: Shixiong Ou Cc: Kees Cook Cc: # v5.9+ Cc: Zsolt Kajtar Reviewed-by: Lucas De Marchi Reviewed-by: Qianqiang Liu Link: https://lore.kernel.org/r/20250922134619.257684-1-tzimmermann@suse.de Signed-off-by: Greg Kroah-Hartman

fbcon: fix integer overflow in fbcon_do_set_font

2025-10-02T11:42:54+00:00

commit 1a194e6c8e1ee745e914b0b7f50fa86c89ed13fe upstream. Fix integer overflow vulnerabilities in fbcon_do_set_font() where font size calculations could overflow when handling user-controlled font parameters. The vulnerabilities occur when: 1. CALC_FONTSZ(h, pitch, charcount) performs h * pith * charcount multiplication with user-controlled values that can overflow. 2. FONT_EXTRA_WORDS * sizeof(int) + size addition can also overflow 3. This results in smaller allocations than expected, leading to buffer overflows during font data copying. Add explicit overflow checking using check_mul_overflow() and check_add_overflow() kernel helpers to safety validate all size calculations before allocation. Signed-off-by: Samasth Norway Ananda Reviewed-by: Thomas Zimmermann Fixes: 39b3cffb8cf3 ("fbcon: prevent user font height or width change from causing potential out-of-bounds access") Cc: George Kennedy Cc: stable Cc: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com Cc: Greg Kroah-Hartman Cc: Simona Vetter Cc: Helge Deller Cc: Thomas Zimmermann Cc: "Ville Syrjälä" Cc: Sam Ravnborg Cc: Qianqiang Liu Cc: Shixiong Ou Cc: Kees Cook Cc: # v5.9+ Signed-off-by: Thomas Zimmermann Link: https://lore.kernel.org/r/20250912170023.3931881-1-samasth.norway.ananda@oracle.com Signed-off-by: Greg Kroah-Hartman

fbdev: Fix vmalloc out-of-bounds write in fast_imageblit

2025-08-28T14:28:31+00:00

commit af0db3c1f898144846d4c172531a199bb3ca375d upstream. This issue triggers when a userspace program does an ioctl FBIOPUT_CON2FBMAP by passing console number and frame buffer number. Ideally this maps console to frame buffer and updates the screen if console is visible. As part of mapping it has to do resize of console according to frame buffer info. if this resize fails and returns from vc_do_resize() and continues further. At this point console and new frame buffer are mapped and sets display vars. Despite failure still it continue to proceed updating the screen at later stages where vc_data is related to previous frame buffer and frame buffer info and display vars are mapped to new frame buffer and eventully leading to out-of-bounds write in fast_imageblit(). This bheviour is excepted only when fg_console is equal to requested console which is a visible console and updates screen with invalid struct references in fbcon_putcs(). Reported-and-tested-by: syzbot+c4b7aa0513823e2ea880@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c4b7aa0513823e2ea880 Signed-off-by: Sravan Kumar Gundu Cc: stable@vger.kernel.org Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbcon: Fix outdated registered_fb reference in comment

2025-08-15T10:08:47+00:00

[ Upstream commit 0f168e7be696a17487e83d1d47e5a408a181080f ] The variable was renamed to fbcon_registered_fb, but this comment was not updated along with the change. Correct it to avoid confusion. Signed-off-by: Shixiong Ou Fixes: efc3acbc105a ("fbcon: Maintain a private array of fb_info") [sima: Add Fixes: line.] Signed-off-by: Simona Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20250709103438.572309-1-oushixiong1025@163.com Signed-off-by: Sasha Levin

tty: vt: make consw::con_switch() return a bool

2025-07-06T09:00:10+00:00

[ Upstream commit 8d5cc8eed738e3202379722295c626cba0849785 ] The non-zero (true) return value from consw::con_switch() means a redraw is needed. So make this return type a bool explicitly instead of int. The latter might imply that -Eerrors are expected. They are not. And document the hook. Signed-off-by: "Jiri Slaby (SUSE)" Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: Daniel Vetter Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linux-parisc@vger.kernel.org Tested-by: Helge Deller # parisc STI console Link: https://lore.kernel.org/r/20240122110401.7289-31-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman Stable-dep-of: 03bcbbb3995b ("dummycon: Trigger redraw when switching consoles with deferred takeover") Signed-off-by: Sasha Levin

tty: vt: sanitize arguments of consw::con_clear()

2025-07-06T09:00:10+00:00

[ Upstream commit 559f01a0ee6d924c6fec3eaf6a5b078b15e71070 ] In consw::con_clear(): * Height is always 1, so drop it. * Offsets and width are always unsigned values, so re-type them as such. This needs a new __fbcon_clear() in the fbcon code to still handle height which might not be 1 when called internally. Note that tests for negative count/width are left in place -- they are taken care of in the next patches. And document the hook. Signed-off-by: "Jiri Slaby (SUSE)" Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: Daniel Vetter Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linux-parisc@vger.kernel.org Tested-by: Helge Deller # parisc STI console Link: https://lore.kernel.org/r/20240122110401.7289-22-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman Stable-dep-of: 03bcbbb3995b ("dummycon: Trigger redraw when switching consoles with deferred takeover") Signed-off-by: Sasha Levin

tty: vt: make init parameter of consw::con_init() a bool

2025-07-06T09:00:10+00:00

[ Upstream commit dae3e6b6180f1a2394b984c596d39ed2c57d25fe ] The 'init' parameter of consw::con_init() is true for the first call of the hook on a particular console. So make the parameter a bool. And document the hook. Signed-off-by: "Jiri Slaby (SUSE)" Reviewed-by: Geert Uytterhoeven Cc: Helge Deller Cc: "James E.J. Bottomley" Cc: Daniel Vetter Cc: linux-fbdev@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linux-parisc@vger.kernel.org Tested-by: Helge Deller # parisc STI console Link: https://lore.kernel.org/r/20240122110401.7289-21-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman Stable-dep-of: 03bcbbb3995b ("dummycon: Trigger redraw when switching consoles with deferred takeover") Signed-off-by: Sasha Levin

fbcon: Make sure modelist not set on unregistered console

2025-06-27T10:08:57+00:00

[ Upstream commit cedc1b63394a866bf8663a3e40f4546f1d28c8d8 ] It looks like attempting to write to the "store_modes" sysfs node will run afoul of unregistered consoles: UBSAN: array-index-out-of-bounds in drivers/video/fbdev/core/fbcon.c:122:28 index -1 is out of range for type 'fb_info *[32]' ... fbcon_info_from_console+0x192/0x1a0 drivers/video/fbdev/core/fbcon.c:122 fbcon_new_modelist+0xbf/0x2d0 drivers/video/fbdev/core/fbcon.c:3048 fb_new_modelist+0x328/0x440 drivers/video/fbdev/core/fbmem.c:673 store_modes+0x1c9/0x3e0 drivers/video/fbdev/core/fbsysfs.c:113 dev_attr_store+0x55/0x80 drivers/base/core.c:2439 static struct fb_info *fbcon_registered_fb[FB_MAX]; ... static signed char con2fb_map[MAX_NR_CONSOLES]; ... static struct fb_info *fbcon_info_from_console(int console) ... return fbcon_registered_fb[con2fb_map[console]]; If con2fb_map contains a -1 things go wrong here. Instead, return NULL, as callers of fbcon_info_from_console() are trying to compare against existing "info" pointers, so error handling should kick in correctly. Reported-by: syzbot+a7d4444e7b6e743572f7@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/679d0a8f.050a0220.163cdc.000c.GAE@google.com/ Signed-off-by: Kees Cook Signed-off-by: Helge Deller Signed-off-by: Sasha Levin