kernel/linux.git/drivers/video/fbdev/core, branch v7.1.12

fbdev: serialize mode sysfs access with lock_fb_info()

2026-08-27T12:34:38+00:00

[ Upstream commit 061db6b7a910b8378f3b2df64f8c0a3ddc6e85f2 ] show_mode(), show_modes(), and store_mode() access fb_info->modelist and fb_info->mode without holding lock_fb_info(). store_modes() takes lock_fb_info() while replacing the modelist and freeing the old one. A concurrent reader or writer can load a pointer to an old modelist entry before store_modes() frees it, then dereference freed memory or store a stale freed pointer in fb_info->mode. Take lock_fb_info() in show_mode(), show_modes(), and store_mode() to serialize with store_modes(). In show_mode(), copy the mode to the stack and format after dropping the lock. In store_mode(), split activate() into a _locked variant to avoid double-locking, and hold the locks for the modelist walk, mode conversion, activation, and fb_info->mode assignment together. Cc: stable@vger.kernel.org # v7.1+ Signed-off-by: Melbin K Mathew Signed-off-by: Helge Deller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fbdev: Wrap user-invoked calls to fb_set_var() in helper

2026-08-27T12:34:38+00:00

[ Upstream commit 6f611e5e5f3327cf2e2daabe6ee5acac58cc784e ] Handle fbcon during display updates in fb_set_var_from_user(). Check with fbcon if the mode change is possible, update hardware state and finally update fbcon. Update all callers. Only the FBIOPUT_VSCREENINFO ioctl currently does all steps. Other mode-changes callers in sysfs and driver code are missing fbcon-related steps. With the new helper, ps3fb and sh_mobile_lcdcfb no longer maintain fbcon state themselves. Signed-off-by: Thomas Zimmermann Signed-off-by: Helge Deller Stable-dep-of: 061db6b7a910 ("fbdev: serialize mode sysfs access with lock_fb_info()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

fbdev: core: Fix pointer desynchronization in fb_io_read()

2026-08-23T12:29:18+00:00

commit 81cc73be40c6f028f1ee3f438ace46afe666dbae upstream. In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to a faulty user buffer), the loop adjusts the chunk size 'c' and updates the remaining 'count'. However, the hardware 'src' pointer has already been eagerly advanced by the original chunk size. If the loop is allowed to continue, the read will resume from an incorrect, over-advanced offset. Since the remaining 'count' was only decremented by the successful bytes, this desynchronization causes the next iterations to execute more hardware reads than originally bounded, eventually leading to out-of-bounds I/O reads. Fix this by breaking out of the loop immediately upon a partial copy_to_user(). A partial copy indicates a faulty user buffer, making subsequent read attempts futile. Breaking out ensures we return the number of successfully read bytes without risking out-of-bounds hardware accesses in subsequent mismatched iterations. Fixes: 6121cd9ef911 ("fbdev: Move I/O read and write code into helper functions") Cc: stable@vger.kernel.org Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn> Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbdev: clear fb_info->mode before deleting a videomode

2026-08-23T12:29:18+00:00

commit 95e647d2a5304a8fd11f1ba3c8502de700650131 upstream. fb_set_var() can delete a mode from info->modelist when userspace passes FB_ACTIVATE_INV_MODE through FBIOPUT_VSCREENINFO. The code checks that the mode being deleted is not the current info->var and that fbcon is not using it, but it does not check fb_info->mode. fb_info->mode may still point into the modelist entry being deleted. If the entry is freed, later mode sysfs reads through show_mode() can dereference a stale pointer. Clear fb_info->mode before calling fb_delete_videomode() when it matches the mode being removed. Cc: stable@vger.kernel.org # v7.1+ Signed-off-by: Melbin K Mathew Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbdev: bound mode sysfs output to the sysfs buffer

2026-08-23T12:29:18+00:00

commit d15d51fb26e830af58f3f21964f1c09c239077ea upstream. mode_string() uses snprintf() which can return a value larger than the remaining buffer space. show_modes() accumulates the return value into i without checking whether i has reached PAGE_SIZE, causing the offset to advance past the sysfs buffer if the modelist is long enough. Add a size parameter to mode_string() and use scnprintf() to return only the bytes actually written. Add an early return when offset already exceeds the buffer. In show_modes(), stop accumulating once the buffer is full. Cc: stable@vger.kernel.org # v7.1+ Signed-off-by: Melbin K Mathew Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbdev: bitblit: bound-check glyph index in bit_cursor()

2026-08-19T16:20:27+00:00

commit e033cbf3975a8465f879ebd5989dc35b04423a4d upstream. bit_cursor() fetches the glyph under the cursor with c = scr_readw(vc_pos); src = vc_font.data + ((c & charmask) * w * height); where charmask is 0x1ff when vc_hi_font_mask is set. The screen buffer value comes directly from scr_readw() and may be larger than the current font's glyph count. Syzkaller triggers this via vcs_write(). The Call Trace shows vcs_write() in vc_screen.c writing an arbitrary 16-bit value with writev() to /dev/vcsa, which vcs_write_buf() in vc_screen.c stores via vcs_scr_writew() without checking charcount. The stored value is later read in bit_cursor() in bitblit.c. When the font is changed from a font with 512 glyphs to a font with 256 glyphs, the screen buffer can retain characters with the high bit set from the previous mode, which could also produce the same out-of-bounds access. BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70 Read of size 16 at addr ffff800086c57970 Call Trace: soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70 bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365 fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427 hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883 update_region+0x100/0x18c drivers/tty/vt/vt.c:669 vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685 bit_putcs_aligned() and bit_putcs_unaligned() already clamp the glyph index to vc_font.charcount. Apply the same clamp in bit_cursor() after extracting the attribute and masking, before indexing fontdata. The fix completes the bounds checking started in commit 18c4ef4e765a ("fbdev: bitblit: bound-check glyph index in bit_putcs*"), which missed the cursor path. This change should be safe because the clamp reuses the existing contract from fbcon: charcount is maintained under console_lock in con_font_set() and fbcon_font_set(), and hi_font_mask is cleared when switching from 512 to 256 glyphs. When stale screen data with high bits remains after a font switch, or when vcs_write() stores an arbitrary value, clamping the index to 0 prevents the out-of-bounds read without changing cursor semantics — the same fallback bit_putcs uses. Reported-by: syzbot+61b1db46218109869c14@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=61b1db46218109869c14 Link: https://lore.kernel.org/all/6a75205c.01d0871a.3a0d52.0032.GAE@google.com/ Fixes: 18c4ef4e765a ("fbdev: bitblit: bound-check glyph index in bit_putcs*") Cc: stable@vger.kernel.org Assisted-by: Hermes:muse-spark-1.2 syzkaller Signed-off-by: Rik van Riel Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbcon: Use correct type for vc_resize() return value

2026-07-24T14:19:01+00:00

commit 84202754fb1727dc3ee87f47104e4162ecc8ba3a upstream. The return value of vc_resize() is int, but fbcon_set_disp() stores it in an unsigned long variable. While the !ret check happens to work correctly by coincidence (negative values become large positive values), the types should match. Use int instead. Eliminates the following W=3 warning: drivers/video/fbdev/core/fbcon.c: In function 'fbcon_set_disp': drivers/video/fbdev/core/fbcon.c:1494:14: warning: implicit conversion from 'int' to 'unsigned long' [-Wconversion] Fixes: af0db3c1f898 ("fbdev: Fix vmalloc out-of-bounds write in fast_imageblit") Cc: stable@vger.kernel.org # v6.17+ Signed-off-by: Jiacheng Yu Reviewed-by: Thomas Zimmermann Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbcon: fix NULL pointer dereference for a console without vc_data

2026-07-24T14:19:01+00:00

commit 5fae9a928482d4845bca169a3a098789203a1ca4 upstream. fbcon_new_modelist() runs when a framebuffer's modelist changes. For each console mapped to it with fb_display[i].mode set, it reads vc_cons[i].d and passes the vc_num to fbcon_set_disp(). This assumes a console with a mode set has a vc_data, but it can be NULL. fbcon_set_disp() sets fb_display[i].mode before it checks vc_data, and fbcon_deinit() leaves the mode set after the vc_data is freed. fbcon_new_modelist() then dereferences the NULL vc_data. Keep fb_display[i].mode set only while the console has a vc_data. Check vc_data before setting the mode in fbcon_set_disp(), and clear the mode in fbcon_deinit(). The existing mode check in fbcon_new_modelist() then skips such consoles. Reported-by: syzbot+42525d636f430fd5d983@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=42525d636f430fd5d983 Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Ian Bridges Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbdev: modedb: Fix misaligned fields in the 1920x1080-60 mode

2026-07-04T11:45:08+00:00

commit d894c48a57d78206e4df9c90d4acfaf39394806a upstream. The 1920x1080@60 modedb entry has one too many initializers before its sync field: a stray "0" occupies the sync slot, which shifts the remaining values by one field. The entry therefore decodes as sync = 0, vmode = FB_SYNC_HOR_HIGH_ACT | FB_SYNC_VERT_HIGH_ACT (0x3, i.e. FB_VMODE_INTERLACED | FB_VMODE_DOUBLE), and flag = FB_VMODE_NONINTERLACED, instead of the intended sync = positive H/V, vmode = non-interlaced. fb_find_mode() then returns a 1920x1080 mode flagged as interlaced + doublescan with active-low syncs. Drivers that honour var->vmode and var->sync when programming display timing enable doublescan and the wrong sync polarity, corrupting the output. Drop the stray initializer so sync and vmode hold their intended values (positive H/V sync, non-interlaced), matching the adjacent 1920x1200 entry. Fixes: c8902258b2b8 ("fbdev: modedb: Add 1920x1080 at 60 Hz video mode") Cc: stable@vger.kernel.org Signed-off-by: Steffen Persvold Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman

fbdev: modedb: fix a possible UAF in fb_find_mode()

2026-07-04T11:45:08+00:00

commit 85b6256469cebdac395e7447147e06b2e151014f upstream. If mode_option is NULL, it is assigned from mode_option_buf: if (!mode_option) { fb_get_options(NULL, &mode_option_buf); mode_option = mode_option_buf; } Later, name is assigned from mode_option: const char *name = mode_option; However, mode_option_buf is freed before name is no longer used: kfree(mode_option_buf); while name is still accessed by: if ((name_matches(db[i], name, namelen) || Since name aliases mode_option_buf, this may result in a use-after-free. Fix this by extending the lifetime of mode_option_buf until the end of the function by using scope-based resource management for cleanup. Signed-off-by: Tuo Li Cc: stable@vger.kernel.org # v6.5+ Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman