[PATCH AUTOSEL 6.15 05/21] NFSv4.2: fix listxattr to return selinux security label

[Sasha Levin <sashal@kernel.org>]

From: Olga Kornievskaia <okorniev@redhat.com>

[ Upstream commit 243fea134633ba3d64aceb4c16129c59541ea2c6 ]

Currently, when NFS is queried for all the labels present on the
file via a command example "getfattr -d -m . /mnt/testfile", it
does not return the security label. Yet when asked specifically for
the label (getfattr -n security.selinux) it will be returned.
Include the security label when all attributes are queried.

Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES** This commit should be backported to stable kernel trees. Here's
my extensive analysis: ## Bug Analysis The commit fixes a clear
functional bug in NFSv4.2's `listxattr` implementation in
`fs/nfs/nfs4proc.c:10853`. When users run `getfattr -d` to list all
extended attributes, the security label (like SELinux context) is
missing from the output, even though it's correctly returned when
specifically requested with `getfattr -n security.selinux`. ## Code
Change Analysis The fix is minimal and well-contained: 1. **Variable
addition**: Adds `error4` to track the security label listing result 2.
**Function call**: Adds `error4 =
security_inode_listsecurity(d_inode(dentry), list, left)` 3. **Pointer
management**: Updates `list` and `left` after `error3` processing
(missing in original) 4. **Total calculation**: Changes `error += error2
+ error3` to `error += error2 + error3 + error4` ## Why This Qualifies
for Backport **1. Clear User-Facing Bug**: The inconsistency between
`getfattr -d` and `getfattr -n security.selinux` affects real-world
usage and user expectations. **2. Minimal Risk**: The change is
architecturally simple - it just adds another xattr source to the
listing function, following the exact same pattern as existing `error2`
and `error3` handling. **3. Follows Existing Patterns**: The commit uses
the same error handling, pointer arithmetic, and function call pattern
established by `nfs4_listxattr_nfs4_label()` and
`nfs4_listxattr_nfs4_user()`. **4. No Feature Addition**: This fixes
existing functionality rather than adding new features. **5. Critical
Subsystem**: Extended attributes and security labels are fundamental for
SELinux environments, making this fix important for security-conscious
deployments. **6. Similar Historical Precedent**: All 5 provided
reference commits with "Backport Status: YES" are NFSv4 security label
fixes with similar characteristics - small, contained bugfixes in the
same subsystem. **7. Contained Scope**: The change is isolated to one
function (`nfs4_listxattr`) in one file, with no cross-subsystem
implications. The fix correctly implements the missing piece: while
`nfs4_listxattr_nfs4_label()` calls `security_inode_listsecurity()` when
`CONFIG_NFS_V4_SECURITY_LABEL` is enabled, the main `nfs4_listxattr()`
function wasn't calling it directly for the general xattr listing case,
creating the inconsistent behavior reported.

 fs/nfs/nfs4proc.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index b1d2122bd5a74..a3a6fc4e3e7f5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -10852,7 +10852,7 @@ const struct nfs4_minor_version_ops *nfs_v4_minor_ops[] = {
 
 static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
 {
-	ssize_t error, error2, error3;
+	ssize_t error, error2, error3, error4;
 	size_t left = size;
 
 	error = generic_listxattr(dentry, list, left);
@@ -10875,8 +10875,16 @@ static ssize_t nfs4_listxattr(struct dentry *dentry, char *list, size_t size)
 	error3 = nfs4_listxattr_nfs4_user(d_inode(dentry), list, left);
 	if (error3 < 0)
 		return error3;
+	if (list) {
+		list += error3;
+		left -= error3;
+	}
+
+	error4 = security_inode_listsecurity(d_inode(dentry), list, left);
+	if (error4 < 0)
+		return error4;
 
-	error += error2 + error3;
+	error += error2 + error3 + error4;
 	if (size && error > size)
 		return -ERANGE;
 	return error;
-- 
2.39.5