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Linux 7.0: posix_acl_to_xattr() now allocates memory

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Kernel devs noted that almost all callers to posix_acl_to_xattr() would
check the ACL value size and allocate a buffer before make the call. To
reduce the repetition, they've changed it to allocate this buffer
internally and return it.

Unfortunately that's not true for us; most of our calls are from
xattr_handler->get() to convert a stored ACL to an xattr, and that call
provides a buffer. For now we have no other option, so this commit
detects the new version and wraps to copy the value back into the
provided buffer and then free it.

Sponsored-by: TrueNAS
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@truenas.com>
Closes #18216
This commit is contained in:
Rob Norris 2026-01-27 16:49:59 +11:00 committed by Brian Behlendorf
parent 204de946eb
commit d34fd6cff3
2 changed files with 48 additions and 0 deletions
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31
config/kernel-acl.m4
View File

@ -22,6 +22,35 @@ AC_DEFUN([ZFS_AC_KERNEL_POSIX_ACL_EQUIV_MODE_WANTS_UMODE_T], [
])
])
dnl #
dnl # 7.0 API change
dnl # posix_acl_to_xattr() now allocates and returns the value.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_POSIX_ACL_TO_XATTR_ALLOC], [
ZFS_LINUX_TEST_SRC([posix_acl_to_xattr_alloc], [
#include <linux/fs.h>
#include <linux/posix_acl_xattr.h>
], [
struct user_namespace *ns = NULL;
struct posix_acl *acl = NULL;
size_t size = 0;
gfp_t gfp = 0;
void *xattr = NULL;
xattr = posix_acl_to_xattr(ns, acl, &size, gfp);
])
])
AC_DEFUN([ZFS_AC_KERNEL_POSIX_ACL_TO_XATTR_ALLOC], [
AC_MSG_CHECKING([whether posix_acl_to_xattr() allocates its result]);
ZFS_LINUX_TEST_RESULT([posix_acl_to_xattr_alloc], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_POSIX_ACL_TO_XATTR_ALLOC, 1,
[posix_acl_to_xattr() allocates its result])
], [
AC_MSG_RESULT(no)
])
])
dnl #
dnl # 3.1 API change,
dnl # Check if inode_operations contains the function get_acl
@ -174,12 +203,14 @@ AC_DEFUN([ZFS_AC_KERNEL_INODE_OPERATIONS_SET_ACL], [
AC_DEFUN([ZFS_AC_KERNEL_SRC_ACL], [
ZFS_AC_KERNEL_SRC_POSIX_ACL_EQUIV_MODE_WANTS_UMODE_T
ZFS_AC_KERNEL_SRC_POSIX_ACL_TO_XATTR_ALLOC
ZFS_AC_KERNEL_SRC_INODE_OPERATIONS_GET_ACL
ZFS_AC_KERNEL_SRC_INODE_OPERATIONS_SET_ACL
])
AC_DEFUN([ZFS_AC_KERNEL_ACL], [
ZFS_AC_KERNEL_POSIX_ACL_EQUIV_MODE_WANTS_UMODE_T
ZFS_AC_KERNEL_POSIX_ACL_TO_XATTR_ALLOC
ZFS_AC_KERNEL_INODE_OPERATIONS_GET_ACL
ZFS_AC_KERNEL_INODE_OPERATIONS_SET_ACL
])

17
include/os/linux/kernel/linux/xattr_compat.h
View File

@ -130,10 +130,27 @@ zpl_acl_from_xattr(const void *value, int size)
return (posix_acl_from_xattr(kcred->user_ns, value, size));
}
/*
* Linux 7.0 API change. posix_acl_to_xattr() changed from filling the
* caller-provided buffer to allocating a buffer with enough space and
* returning it. We wrap this up by copying the result into the provided
* buffer and freeing the allocated buffer.
*/
static inline int
zpl_acl_to_xattr(struct posix_acl *acl, void *value, int size)
{
#ifdef HAVE_POSIX_ACL_TO_XATTR_ALLOC
size_t s = 0;
void *v = posix_acl_to_xattr(kcred->user_ns, acl, &s,
kmem_flags_convert(KM_SLEEP));
if (v == NULL)
return (-ENOMEM);
memcpy(value, v, MIN(size, s));
kfree(v);
return (0);
#else
return (posix_acl_to_xattr(kcred->user_ns, acl, value, size));
#endif
}
#endif /* _ZFS_XATTR_H */