[PATCH v2 0/2] selinux: Don't ignore ENOENT in Permissive mode
v2 of: https://listman.redhat.com/archives/libvir-list/2021-September/msg00553.html diff to v1: - Reworded commit message in 2/2. Michal Prívozník (2): selinux: Swap two blocks handling setfilecon_raw() failure selinux: Don't ignore ENOENT in Permissive mode src/security/security_selinux.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) -- 2.32.0
In virSecuritySELinuxSetFileconImpl() we have code that handles setfilecon_raw() failure. The code consists of two blocks: one for dealing with shared filesystem like NFS (errno is ENOTSUP or EROFS) and the other block that's dealing with EPERM for privileged daemon. Well, the order of these two blocks is a bit confusing because the comment above them mentions the NFS case but EPERM block follows. Swap these two blocks to make it less confusing. Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/security/security_selinux.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-) diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c index 622a8f4c02..39c10cbe8f 100644 --- a/src/security/security_selinux.c +++ b/src/security/security_selinux.c @@ -1264,22 +1264,9 @@ virSecuritySELinuxSetFileconImpl(const char *path, * boolean tunables to allow it ... */ VIR_WARNINGS_NO_WLOGICALOP_EQUAL_EXPR - if (setfilecon_errno != EOPNOTSUPP && setfilecon_errno != ENOTSUP && - setfilecon_errno != EROFS) { + if (setfilecon_errno == EOPNOTSUPP || setfilecon_errno == ENOTSUP || + setfilecon_errno == EROFS) { VIR_WARNINGS_RESET - /* However, don't claim error if SELinux is in Enforcing mode and - * we are running as unprivileged user and we really did see EPERM. - * Otherwise we want to return error if SELinux is Enforcing. */ - if (security_getenforce() == 1 && - (setfilecon_errno != EPERM || privileged)) { - virReportSystemError(setfilecon_errno, - _("unable to set security context '%s' on '%s'"), - tcon, path); - return -1; - } - VIR_WARN("unable to set security context '%s' on '%s' (errno %d)", - tcon, path, setfilecon_errno); - } else { const char *msg; if (virFileIsSharedFSType(path, VIR_FILE_SHFS_NFS) == 1 && security_get_boolean_active("virt_use_nfs") != 1) { @@ -1293,6 +1280,19 @@ virSecuritySELinuxSetFileconImpl(const char *path, VIR_INFO("Setting security context '%s' on '%s' not supported", tcon, path); } + } else { + /* However, don't claim error if SELinux is in Enforcing mode and + * we are running as unprivileged user and we really did see EPERM. + * Otherwise we want to return error if SELinux is Enforcing. */ + if (security_getenforce() == 1 && + (setfilecon_errno != EPERM || privileged)) { + virReportSystemError(setfilecon_errno, + _("unable to set security context '%s' on '%s'"), + tcon, path); + return -1; + } + VIR_WARN("unable to set security context '%s' on '%s' (errno %d)", + tcon, path, setfilecon_errno); } return 1; -- 2.32.0
In selinux driver there's virSecuritySELinuxSetFileconImpl() which is responsible for actual setting of SELinux label on given file and handling possible failures. In fhe failure handling code we decide whether failure is fatal or not. But there is a bug: depending on SELinux mode (Permissive vs. Enforcing) the ENOENT is either ignored or considered fatal. This not correct - ENOENT must always be fatal for couple of reasons: - In virSecurityStackTransactionCommit() the seclabels are set for individual secdrivers (e.g. SELinux first and then DAC), but if one secdriver succeeds and another one fails, then no rollback is performed for the successful one leaking remembered labels. - QEMU would fail opening the file anyways (if neither of secdrivers reported error and thus cancelled domain startup) Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2004850 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/security/security_selinux.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c index 39c10cbe8f..a3b5fa7546 100644 --- a/src/security/security_selinux.c +++ b/src/security/security_selinux.c @@ -1283,9 +1283,11 @@ virSecuritySELinuxSetFileconImpl(const char *path, } else { /* However, don't claim error if SELinux is in Enforcing mode and * we are running as unprivileged user and we really did see EPERM. - * Otherwise we want to return error if SELinux is Enforcing. */ - if (security_getenforce() == 1 && - (setfilecon_errno != EPERM || privileged)) { + * Otherwise we want to return error if SELinux is Enforcing, or we + * saw EPERM regardless of SELinux mode. */ + if (setfilecon_errno == ENOENT || + (security_getenforce() == 1 && + (setfilecon_errno != EPERM || privileged))) { virReportSystemError(setfilecon_errno, _("unable to set security context '%s' on '%s'"), tcon, path); -- 2.32.0
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Michal Privoznik