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selinux: fix inconsistency between inode_getxattr and inode_listsecurity

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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: c8e222616c ("selinux: allow reading labels before policy is loaded")
Cc: stable@vger.kernel.org#v5.9+
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Amir Goldstein 2020-12-19 12:05:27 +02:00 committed by Paul Moore
parent 95ca90726e
commit a9ffe682c5
1 changed files with 4 additions and 0 deletions
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4
security/selinux/hooks.c
View File

@ -3414,6 +3414,10 @@ 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;