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[58.152.109.154]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beca535bc1sm71381615ad.56.2026.05.26.02.15.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 02:15:19 -0700 (PDT) From: Tuo Li To: simona@ffwll.ch, deller@gmx.de, kees@kernel.org, tzimmermann@suse.de Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Tuo Li Subject: [PATCH] fbdev:modedb: fix a possible UAF in fb_find_mode() Date: Tue, 26 May 2026 17:15:07 +0800 Message-ID: <20260526091507.421730-1-islituo@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" If mode_option is NULL, it is assigned from mode_option_buf: if (!mode_option) { fb_get_options(NULL, &mode_option_buf); mode_option =3D mode_option_buf; } Later, name is assigned from mode_option: const char *name =3D 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 moving the kfree(mode_option_buf) call behind the access, and add corresponding cleanup before early returns. Signed-off-by: Tuo Li --- drivers/video/fbdev/core/modedb.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/video/fbdev/core/modedb.c b/drivers/video/fbdev/core/m= odedb.c index 703d0b7aec32..91f6c78f9e19 100644 --- a/drivers/video/fbdev/core/modedb.c +++ b/drivers/video/fbdev/core/modedb.c @@ -724,7 +724,6 @@ int fb_find_mode(struct fb_var_screeninfo *var, res_specified =3D 1; } done: - kfree(mode_option_buf); if (cvt) { struct fb_videomode cvt_mode; int ret; @@ -749,6 +748,7 @@ int fb_find_mode(struct fb_var_screeninfo *var, =20 if (!ret && !fb_try_mode(var, info, &cvt_mode, bpp)) { DPRINTK("modedb CVT: CVT mode ok\n"); + kfree(mode_option_buf); return 1; } =20 @@ -793,8 +793,10 @@ int fb_find_mode(struct fb_var_screeninfo *var, if (!interlace_specified || db_interlace =3D=3D interlace) if (refresh_specified && - db[i].refresh =3D=3D refresh) + db[i].refresh =3D=3D refresh) { + kfree(mode_option_buf); return 1; + } =20 if (score < diff) { diff =3D score; @@ -802,6 +804,8 @@ int fb_find_mode(struct fb_var_screeninfo *var, } } } + + kfree(mode_option_buf); if (best !=3D -1) { fb_try_mode(var, info, &db[best], bpp); return (refresh_specified) ? 2 : 1; --=20 2.43.0