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Tue, 27 Oct 2026 08:16:44 -0700 (PDT) Received: from localhost.localdomain ([14.116.239.40]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-850f8458d7fsm10768970a34.2.2026.10.27.08.16.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Oct 2026 08:16:43 -0700 (PDT) From: Henry Martin To: Konstantin Komarov Cc: ntfs3@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Henry Martin , stable@vger.kernel.org Subject: [PATCH] fs/ntfs3: fix NULL deref in ni_std5() on stream inodes Date: Tue, 27 Oct 2026 23:16:15 +0800 Message-ID: <20261027151615.971171-2-bsdhenrymartin@gmail.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20261027151615.971171-1-bsdhenrymartin@gmail.com> References: <20261027151615.971171-1-bsdhenrymartin@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ni_std5() looks up the standard information attribute in the inode's own MFT record: attr = mi_find_attr(ni, &ni->mi, NULL, ATTR_STD, NULL, 0, NULL); without redirecting to the base inode. For an ADS stream inode, ni->mi.mrec is never initialized (ntfs_init_ads_node() in fs/ntfs3/inode.c leaves mi.mrec NULL), so mi_find_attr() -> mi_enum_attr() dereferences rec == NULL: BUG: unable to handle kernel NULL pointer dereference RIP: mi_enum_attr+0x18/0x180 The SYSTEM_NTFS_SECURITY xattr path calls ni_std5() without a guard for stream inodes (fs/ntfs3/xattr.c): ntfs_set_acl()/ntfs_xattr_set() reach it via ntfs_insert_security -> ni_lock(ni) -> ni_std5(ni) on the stream inode, and the stream inode inherits the base's i_mode/uid/gid, so the may_write_xattr() ownership check passes for the file owner. The default stream-name parsing (colons) is enabled, so an unprivileged local user can open("file:stream"), set the security descriptor xattr on it and panic the kernel. Redirect stream inodes to their base record in ni_std5(). This issue was discovered by Tencent CodeBuddy Security. Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations") Cc: stable@vger.kernel.org Signed-off-by: Henry Martin --- fs/ntfs3/frecord.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c index bead01a953f3f..dce6400195aee 100644 --- a/fs/ntfs3/frecord.c +++ b/fs/ntfs3/frecord.c @@ -89,6 +89,13 @@ struct ATTR_STD_INFO5 *ni_std5(struct ntfs_inode *ni) { const struct ATTRIB *attr; + /* Stream inodes have no MFT record of their own (mi.mrec is + * NULL); the standard information attribute lives in the base + * record. + */ + if (ni->base && ni->base != ni) + ni = ni->base; + attr = mi_find_attr(ni, &ni->mi, NULL, ATTR_STD, NULL, 0, NULL); return attr ? resident_data_ex(attr, sizeof(struct ATTR_STD_INFO5)) : -- 2.43.7