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Wed, 01 Jul 2026 16:42:58 -0700 (PDT) Received: from localhost.localdomain ([2a01:4f9:2a:1c13::2]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-39b37fda160sm2836261fa.29.2026.07.01.16.42.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2026 16:42:56 -0700 (PDT) From: Melbin K Mathew To: deller@gmx.de Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Melbin K Mathew , stable@vger.kernel.org Subject: [PATCH v3 2/3] fbdev: clear fb_info->mode before deleting a videomode Date: Thu, 2 Jul 2026 01:42:47 +0200 Message-Id: <20260701234248.236023-3-mlbnkm1@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260701231706.234715-1-mlbnkm1@gmail.com> References: <20260701231706.234715-1-mlbnkm1@gmail.com> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Melbin K Mathew --- drivers/video/fbdev/core/fbmem.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 2f1c56e5a7..c8aa163b0e 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -246,8 +246,11 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) ret = fb_mode_is_equal(&mode1, &mode2); if (!ret) { ret = fbcon_mode_deleted(info, &mode1); - if (!ret) + if (!ret) { + if (info->mode && fb_mode_is_equal(info->mode, &mode1)) + info->mode = NULL; fb_delete_videomode(&mode1, &info->modelist); + } } return ret ? -EINVAL : 0; -- 2.39.5