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Hallyn" , linux-security-module@vger.kernel.org (open list:SECURITY SUBSYSTEM), linux-kernel@vger.kernel.org (open list) Subject: [PATCH] ima: don't clear IMA_DIGSIG flag when setting non-IMA xattr Date: Tue, 2 Sep 2025 12:25:14 +0800 Message-ID: <20250902042515.759750-1-coxu@redhat.com> X-Mailer: git-send-email 2.51.0 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" Currently when both IMA and EVM are in fix mode, the IMA signature will be reset to IMA hash if a program first stores IMA signature in security.ima and then sets security.selinux for a file. For example, on Fedora, after booting the kernel with "ima_appraise=3Dfix evm=3Dfix ima_policy=3Dappraise_tcb" and installing rpm-plugin-ima, reinstalling a package will not make good reference IMA signature generated. Instead IMA hash is generated, # getfattr -m - -d -e hex /usr/bin/bash # file: usr/bin/bash security.ima=3D0x0404... This happens because when setting selinux.selinux, the IMA_DIGSIG flag that had been set early was cleared. As a result, IMA hash is generated when the file is closed. Here's a minimal C reproducer, #include #include #include #include #include #include int main() { const char* file_path =3D "/usr/sbin/test_binary"; const char* hex_string =3D "030204d33204490066306402304"; int length =3D strlen(hex_string); char* ima_attr_value; int fd; fd =3D open(file_path, O_WRONLY|O_CREAT|O_EXCL, 0644); if (fd =3D=3D -1) { perror("Error opening file"); return 1; } ima_attr_value =3D (char*)malloc(length / 2 ); for (int i =3D 0, j =3D 0; i < length; i +=3D 2, j++) { sscanf(hex_string + i, "%2hhx", &ima_attr_value[j]); } if (fsetxattr(fd, "security.ima", ima_attr_value, length/2, 0) =3D= =3D -1) { perror("Error setting extended attribute"); close(fd); return 1; } const char* selinux_value=3D "system_u:object_r:bin_t:s0"; if (fsetxattr(fd, "security.selinux", selinux_value, strlen(selinux= _value), 0) =3D=3D -1) { perror("Error setting extended attribute"); close(fd); return 1; } close(fd); return 0; } Signed-off-by: Coiby Xu --- security/integrity/ima/ima_appraise.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima= /ima_appraise.c index f435eff4667f..fc82161f8b30 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -708,7 +708,7 @@ static void ima_reset_appraise_flags(struct inode *inod= e, int digsig) set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); if (digsig) set_bit(IMA_DIGSIG, &iint->atomic_flags); - else + else if (digsig !=3D -1) clear_bit(IMA_DIGSIG, &iint->atomic_flags); } =20 @@ -794,6 +794,8 @@ static int ima_inode_setxattr(struct mnt_idmap *idmap, = struct dentry *dentry, digsig =3D (xvalue->type =3D=3D EVM_IMA_XATTR_DIGSIG); } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) { digsig =3D (xvalue->type =3D=3D EVM_XATTR_PORTABLE_DIGSIG); + } else if (result !=3D 1) { + digsig =3D -1; } if (result =3D=3D 1 || evm_revalidate_status(xattr_name)) { ima_reset_appraise_flags(d_backing_inode(dentry), digsig); --=20 2.51.0