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[58.152.109.39]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-842820e8e6asm22196451b3a.0.2026.06.09.19.50.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2026 19:50:25 -0700 (PDT) From: Tuo Li To: simona@ffwll.ch, deller@gmx.de, tzimmermann@suse.de, kees@kernel.org Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Tuo Li Subject: [PATCH v2] fbdev:modedb: fix a possible UAF in fb_find_mode() Date: Wed, 10 Jun 2026 10:50:14 +0800 Message-ID: <20260610025014.5913-1-islituo@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 and using scope-based resource management for cleanup. Signed-off-by: Tuo Li --- v2: * Use scope-based resource management instead of manual kfree() calls. Thanks to Helge Deller for the helpful advice. --- drivers/video/fbdev/core/modedb.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/video/fbdev/core/modedb.c b/drivers/video/fbdev/core/modedb.c index 703d0b7aec32..b6926764a99c 100644 --- a/drivers/video/fbdev/core/modedb.c +++ b/drivers/video/fbdev/core/modedb.c @@ -626,7 +626,7 @@ int fb_find_mode(struct fb_var_screeninfo *var, const struct fb_videomode *default_mode, unsigned int default_bpp) { - char *mode_option_buf = NULL; + char *mode_option_buf __free(kfree) = NULL; int i; /* Set up defaults */ @@ -724,7 +724,6 @@ int fb_find_mode(struct fb_var_screeninfo *var, res_specified = 1; } done: - kfree(mode_option_buf); if (cvt) { struct fb_videomode cvt_mode; int ret; -- 2.43.0