git: 18d1c86788f6 - main - linux(4): Fix listxattr for the case when the size is 0

The branch main has been updated by dchagin:

URL: https://cgit.FreeBSD.org/src/commit/?id=18d1c86788f66f42c4e096142f4f8d168f68732c

commit 18d1c86788f66f42c4e096142f4f8d168f68732c
Author:     Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2023-09-05 08:51:46 +0000
Commit:     Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2023-09-05 08:51:46 +0000

    linux(4): Fix listxattr for the case when the size is 0
    
    If size is specified as zero, these calls return the current size
    of the list of extended attribute names (and leave list unchanged).
    
    Tested by:              zirias
    MFC after:              1 week
---
 sys/compat/linux/linux_xattr.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/sys/compat/linux/linux_xattr.c b/sys/compat/linux/linux_xattr.c
index 74b47f1cbaec..71d7ae58439e 100644
--- a/sys/compat/linux/linux_xattr.c
+++ b/sys/compat/linux/linux_xattr.c
@@ -173,24 +173,28 @@ listxattr(struct thread *td, struct listxattr_args *args)
 		while (rs > 0) {
 			keylen = (unsigned char)key[0];
 			pairlen = prefixlen + 1 + keylen + 1;
-			if (cnt + pairlen > LINUX_XATTR_LIST_MAX) {
+			cnt += pairlen;
+			if (cnt > LINUX_XATTR_LIST_MAX) {
 				error = E2BIG;
 				break;
 			}
-			if ((args->list != NULL && cnt > args->size) ||
+			/*
+			 * If size is specified as zero, return the current size
+			 * of the list of extended attribute names.
+			 */
+			if ((args->size > 0 && cnt > args->size) ||
 			    pairlen >= sizeof(attrname)) {
 				error = ERANGE;
 				break;
 			}
 			++key;
-			if (args->list != NULL) {
+			if (args->list != NULL && args->size > 0) {
 				sprintf(attrname, "%s.%.*s", prefix, keylen, key);
 				error = copyout(attrname, args->list, pairlen);
 				if (error != 0)
 					break;
 				args->list += pairlen;
 			}
-			cnt += pairlen;
 			key += keylen;
 			rs -= (keylen + 1);
 		}