| Message ID | 20201219100527.16060-1-amir73il@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | selinux: fix inconsistency between inode_getxattr and inode_listsecurity | expand |
On Sat, Dec 19, 2020 at 11:07 AM Amir Goldstein <amir73il@gmail.com> wrote: > When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr > calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will > intercept in inode_getxattr hooks. > > When selinux LSM is installed but not initialized, it will list the > security.selinux xattr in inode_listsecurity, but will not intercept it > in inode_getxattr. This results in -ENODATA for a getxattr call for an > xattr returned by listxattr. > > This situation was manifested as overlayfs failure to copy up lower > files from squashfs when selinux is built-in but not initialized, > because ovl_copy_xattr() iterates the lower inode xattrs by > vfs_listxattr() and vfs_getxattr(). > > Match the logic of inode_listsecurity to that of inode_getxattr and > do not list the security.selinux xattr if selinux is not initialized. > > Reported-by: Michael Labriola <michael.d.labriola@gmail.com> > Tested-by: Michael Labriola <michael.d.labriola@gmail.com> > Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/ > Fixes: c8e222616c7e ("selinux: allow reading labels before policy is loaded") > Cc: stable@vger.kernel.org#v5.9+ > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > --- > security/selinux/hooks.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 6b1826fc3658..e132e082a5af 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -3406,6 +3406,10 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name, > static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) > { > const int len = sizeof(XATTR_NAME_SELINUX); > + > + if (!selinux_initialized(&selinux_state)) > + return 0; > + > if (buffer && len <= buffer_size) > memcpy(buffer, XATTR_NAME_SELINUX, len); > return len; > -- > 2.25.1 Looked at the logic in vfs_listxattr() and this looks reasonable. Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com> Thank you for the patch!
On Mon, Jan 4, 2021 at 4:39 AM Ondrej Mosnacek <omosnace@redhat.com> wrote: > On Sat, Dec 19, 2020 at 11:07 AM Amir Goldstein <amir73il@gmail.com> wrote: > > When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr > > calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will > > intercept in inode_getxattr hooks. > > > > When selinux LSM is installed but not initialized, it will list the > > security.selinux xattr in inode_listsecurity, but will not intercept it > > in inode_getxattr. This results in -ENODATA for a getxattr call for an > > xattr returned by listxattr. > > > > This situation was manifested as overlayfs failure to copy up lower > > files from squashfs when selinux is built-in but not initialized, > > because ovl_copy_xattr() iterates the lower inode xattrs by > > vfs_listxattr() and vfs_getxattr(). > > > > Match the logic of inode_listsecurity to that of inode_getxattr and > > do not list the security.selinux xattr if selinux is not initialized. > > > > Reported-by: Michael Labriola <michael.d.labriola@gmail.com> > > Tested-by: Michael Labriola <michael.d.labriola@gmail.com> > > Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/ > > Fixes: c8e222616c7e ("selinux: allow reading labels before policy is loaded") > > Cc: stable@vger.kernel.org#v5.9+ > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > --- > > security/selinux/hooks.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > index 6b1826fc3658..e132e082a5af 100644 > > --- a/security/selinux/hooks.c > > +++ b/security/selinux/hooks.c > > @@ -3406,6 +3406,10 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name, > > static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) > > { > > const int len = sizeof(XATTR_NAME_SELINUX); > > + > > + if (!selinux_initialized(&selinux_state)) > > + return 0; > > + > > if (buffer && len <= buffer_size) > > memcpy(buffer, XATTR_NAME_SELINUX, len); > > return len; > > -- > > 2.25.1 > > Looked at the logic in vfs_listxattr() and this looks reasonable. Agreed, this looks good to me too; I'll merge it into selinux/next. Thanks everyone!
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 6b1826fc3658..e132e082a5af 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3406,6 +3406,10 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name, static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) { const int len = sizeof(XATTR_NAME_SELINUX); + + if (!selinux_initialized(&selinux_state)) + return 0; + if (buffer && len <= buffer_size) memcpy(buffer, XATTR_NAME_SELINUX, len); return len;