git: 1bfc4574f786 - main - linux(4): Return ENOTSUP from xattr syscalls instead of EPERM

The branch main has been updated by dchagin:

URL: https://cgit.FreeBSD.org/src/commit/?id=1bfc4574f78653e4b64ac9dd31518c96a17fe52b

commit 1bfc4574f78653e4b64ac9dd31518c96a17fe52b
Author:     Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2023-09-01 08:11:02 +0000
Commit:     Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2023-09-01 08:11:02 +0000

    linux(4): Return ENOTSUP from xattr syscalls instead of EPERM
    
    FreeBSD does not permits manipulating extended attributes in the system
    namespace by unprivileged accounts, even if account has appropriate
    privileges to access filesystem object.
    In Linux the system namespace is used to preserve posix acls. Some Gnu
    coreutils binaries uses posix acls, eg, install, ls.  And fails if we
    unexpectedly return EPERM error from xattr system calls.
    
    In the other hands, in Linux read and write access to the system
    namespace depend on the policy implemented for each filesystem, so we'll
    mimics we're a filesystem that prohibits this for unpriveleged accounts.
    
    Reported by:            zirias
    Tested by:              zirias
    MFC after:              1 week
---
 sys/compat/linux/linux_xattr.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/sys/compat/linux/linux_xattr.c b/sys/compat/linux/linux_xattr.c
index 2b46cf708c7d..74b47f1cbaec 100644
--- a/sys/compat/linux/linux_xattr.c
+++ b/sys/compat/linux/linux_xattr.c
@@ -87,6 +87,16 @@ struct removexattr_args {
 static char *extattr_namespace_names[] = EXTATTR_NAMESPACE_NAMES;
 
 
+static int
+error_to_xattrerror(int attrnamespace, int error)
+{
+
+	if (attrnamespace == EXTATTR_NAMESPACE_SYSTEM && error == EPERM)
+		return (ENOTSUP);
+	else
+		return (error);
+}
+
 static int
 xatrr_to_extattr(const char *uattrname, int *attrnamespace, char *attrname)
 {
@@ -188,7 +198,7 @@ listxattr(struct thread *td, struct listxattr_args *args)
 	if (error == 0)
 		td->td_retval[0] = cnt;
 	free(data, M_LINUX);
-	return (error);
+	return (error_to_xattrerror(attrnamespace, error));
 }
 
 int
@@ -248,7 +258,7 @@ removexattr(struct thread *td, struct removexattr_args *args)
 	else
 		error = kern_extattr_delete_fd(td, args->fd, attrnamespace,
 		    attrname);
-	return (error);
+	return (error_to_xattrerror(attrnamespace, error));
 }
 
 int
@@ -392,7 +402,7 @@ setxattr(struct thread *td, struct setxattr_args *args)
 		    attrname, args->value, args->size);
 out:
 	td->td_retval[0] = 0;
-	return (error);
+	return (error_to_xattrerror(attrnamespace, error));
 }
 
 int