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([121.185.186.233]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-33b626d61aasm12295067a91.17.2025.10.13.06.47.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Oct 2025 06:47:26 -0700 (PDT) From: Jeongjun Park To: Namjae Jeon , Sungjong Seo Cc: Yuezhang Mo , Al Viro , pali@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, syzbot+98cc76a76de46b3714d4@syzkaller.appspotmail.com, Jeongjun Park Subject: [PATCH v3] exfat: fix out-of-bounds in exfat_nls_to_ucs2() Date: Mon, 13 Oct 2025 22:47:08 +0900 Message-Id: <20251013134708.1270704-1-aha310510@gmail.com> X-Mailer: git-send-email 2.34.1 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" Since the len argument value passed to exfat_ioctl_set_volume_label() from exfat_nls_to_utf16() is passed 1 too large, an out-of-bounds read occurs when dereferencing p_cstring in exfat_nls_to_ucs2() later. And because of the NLS_NAME_OVERLEN macro, another error occurs when creating a file with a period at the end using utf8 and other iocharsets, so the NLS_NAME_OVERLEN macro should be removed and the len argument value should be passed as FSLABEL_MAX - 1. Cc: Reported-by: syzbot+98cc76a76de46b3714d4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D98cc76a76de46b3714d4 Fixes: 370e812b3ec1 ("exfat: add nls operations") Signed-off-by: Jeongjun Park --- fs/exfat/file.c | 2 +- fs/exfat/nls.c | 3 --- 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/fs/exfat/file.c b/fs/exfat/file.c index f246cf439588..7ce0fb6f2564 100644 --- a/fs/exfat/file.c +++ b/fs/exfat/file.c @@ -521,7 +521,7 @@ static int exfat_ioctl_set_volume_label(struct super_bl= ock *sb, =20 memset(&uniname, 0, sizeof(uniname)); if (label[0]) { - ret =3D exfat_nls_to_utf16(sb, label, FSLABEL_MAX, + ret =3D exfat_nls_to_utf16(sb, label, FSLABEL_MAX - 1, &uniname, &lossy); if (ret < 0) return ret; diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c index 8243d94ceaf4..57db08a5271c 100644 --- a/fs/exfat/nls.c +++ b/fs/exfat/nls.c @@ -616,9 +616,6 @@ static int exfat_nls_to_ucs2(struct super_block *sb, unilen++; } =20 - if (p_cstring[i] !=3D '\0') - lossy |=3D NLS_NAME_OVERLEN; - *uniname =3D '\0'; p_uniname->name_len =3D unilen; p_uniname->name_hash =3D exfat_calc_chksum16(upname, unilen << 1, 0, --