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Switch to .get_inode_acl() to avoid rcu corruption.

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In el9.6, the kernel VFS no longer goes through xattr handlers to
retreive ACLs, but instead calls the FS drivers' .get_{inode_}acl
method.  In the initial compat version we hooked up to .get_acl given
the identical name that was used in the past.

However, this results in caching issues, as was encountered by customers
and exposed in the added test case `basic-acl-consistency`. The result
is that some group ACL entries may appear randomly missing. Dropping
caches may temporarily fix the issue.

The root cause of the issue is that the VFS now has 2 separate paths to
retreive ACL's from the FS driver, and, they have conflicting
implications for caching. `.get_acl` is purely meant for filesystems
like overlay/ecryptfs where no caching should ever go on as they are
fully passthrough only. Filesystems with dentries (i.e. all normal
filesystems should not expose this interface, and instead expose the
.get_inode_acl method. And indeed, in introducing the new interface, the
upstream kernel converts all but a few fs's to use .get_inode_acl().

The functional change in the driver is to detach KC_GET_ACL_DENTRY and
introduce KC_GET_INODE_ACL to handle the new (and required) interface.
KC_SET_ACL_DENTRY is detached due to it being a different changeset in
the kernel and we should separate these for good measure now.

Signed-off-by: Auke Kok <auke.kok@versity.com>
This commit is contained in:
Auke Kok
2026-01-22 12:21:15 -08:00
parent 0ef22b3c44
commit 533f309aec
5 changed files with 54 additions and 23 deletions
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20
kmod/src/Makefile.kernelcompat
View File

@@ -479,10 +479,20 @@ ifneq (,$(shell grep '^unsigned int stack_trace_save' include/linux/stacktrace.h
ccflags-y += -DKC_STACK_TRACE_SAVE
endif
# v6.1-rc1-4-g7420332a6ff4
#
# .get_acl() method now has dentry arg (and mnt_idmap). The old get_acl has been renamed
# to get_inode_acl() and is still available as well, but has an extra rcu param.
ifneq (,$(shell grep 'struct posix_acl ...get_acl..struct mnt_idmap ., struct dentry' include/linux/fs.h))
ccflags-y += -DKC_GET_ACL_DENTRY
# v6.1-rc1-2-g138060ba92b3
#
# set_acl now passed a struct dentry instead of inode.
#
ifneq (,$(shell grep 'int ..set_acl.*struct dentry' include/linux/fs.h))
ccflags-y += -DKC_SET_ACL_DENTRY
endif
#
# v6.1-rc1-3-gcac2f8b8d8b5
#
# get_acl renamed to get_inode_acl.
#
ifneq (,$(shell grep 'struct posix_acl.*get_inode_acl' include/linux/fs.h))
ccflags-y += -DKC_GET_INODE_ACL
endif

23
kmod/src/acl.c
View File

@@ -107,20 +107,22 @@ struct posix_acl *scoutfs_get_acl_locked(struct inode *inode, int type, struct s
return acl;
}
#ifdef KC_GET_ACL_DENTRY
struct posix_acl *scoutfs_get_acl(KC_VFS_NS_DEF
struct dentry *dentry, int type)
{
struct inode *inode = dentry->d_inode;
#ifdef KC_GET_INODE_ACL
struct posix_acl *scoutfs_get_acl(struct inode *inode, int type, bool rcu)
#else
struct posix_acl *scoutfs_get_acl(struct inode *inode, int type)
{
#endif
{
struct super_block *sb = inode->i_sb;
struct scoutfs_lock *lock = NULL;
struct posix_acl *acl;
int ret;
#ifdef KC_GET_INODE_ACL
if (rcu)
return ERR_PTR(-ECHILD);
#endif
#ifndef KC___POSIX_ACL_CREATE
if (!IS_POSIXACL(inode))
return NULL;
@@ -208,7 +210,7 @@ out:
return ret;
}
#ifdef KC_GET_ACL_DENTRY
#ifdef KC_SET_ACL_DENTRY
int scoutfs_set_acl(KC_VFS_NS_DEF
struct dentry *dentry, struct posix_acl *acl, int type)
{
@@ -254,9 +256,8 @@ int scoutfs_acl_get_xattr(struct dentry *dentry, const char *name, void *value,
if (!IS_POSIXACL(dentry->d_inode))
return -EOPNOTSUPP;
#ifdef KC_GET_ACL_DENTRY
acl = scoutfs_get_acl(KC_VFS_INIT_NS
dentry, type);
#ifdef KC_GET_INODE_ACL
acl = scoutfs_get_acl(dentry->d_inode, type, false);
#else
acl = scoutfs_get_acl(dentry->d_inode, type);
#endif
@@ -305,7 +306,7 @@ int scoutfs_acl_set_xattr(struct dentry *dentry, const char *name, const void *v
}
}
#ifdef KC_GET_ACL_DENTRY
#ifdef KC_SET_ACL_DENTRY
ret = scoutfs_set_acl(KC_VFS_INIT_NS dentry, acl, type);
#else
ret = scoutfs_set_acl(dentry->d_inode, acl, type);

12
kmod/src/acl.h
View File

@@ -1,12 +1,16 @@
#ifndef _SCOUTFS_ACL_H_
#define _SCOUTFS_ACL_H_
#ifdef KC_GET_ACL_DENTRY
struct posix_acl *scoutfs_get_acl(KC_VFS_NS_DEF struct dentry *dentry, int type);
int scoutfs_set_acl(KC_VFS_NS_DEF struct dentry *dentry, struct posix_acl *acl, int type);
#ifdef KC_SET_ACL_DENTRY
int scoutfs_set_acl(KC_VFS_NS_DEF
struct dentry *dentry, struct posix_acl *acl, int type);
#else
int scoutfs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
#endif
#ifdef KC_GET_INODE_ACL
struct posix_acl *scoutfs_get_acl(struct inode *inode, int type, bool rcu);
#else
struct posix_acl *scoutfs_get_acl(struct inode *inode, int type);
int scoutfs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
#endif
struct posix_acl *scoutfs_get_acl_locked(struct inode *inode, int type, struct scoutfs_lock *lock);
int scoutfs_set_acl_locked(struct inode *inode, struct posix_acl *acl, int type,

10
kmod/src/dir.c
View File

@@ -2006,7 +2006,11 @@ const struct inode_operations scoutfs_symlink_iops = {
#ifdef KC_LINUX_HAVE_RHEL_IOPS_WRAPPER
.removexattr = generic_removexattr,
#endif
#ifdef KC_GET_INODE_ACL
.get_inode_acl = scoutfs_get_acl,
#else
.get_acl = scoutfs_get_acl,
#endif
#ifndef KC_LINUX_HAVE_RHEL_IOPS_WRAPPER
.tmpfile = scoutfs_tmpfile,
.rename = scoutfs_rename_common,
@@ -2052,8 +2056,12 @@ const struct inode_operations scoutfs_dir_iops = {
.removexattr = generic_removexattr,
#endif
.listxattr = scoutfs_listxattr,
#ifdef KC_GET_INODE_ACL
.get_inode_acl = scoutfs_get_acl,
#else
.get_acl = scoutfs_get_acl,
#ifdef KC_GET_ACL_DENTRY
#endif
#ifdef KC_SET_ACL_DENTRY
.set_acl = scoutfs_set_acl,
#endif
.symlink = scoutfs_symlink,

12
kmod/src/inode.c
View File

@@ -149,8 +149,12 @@ static const struct inode_operations scoutfs_file_iops = {
.removexattr = generic_removexattr,
#endif
.listxattr = scoutfs_listxattr,
#ifdef KC_GET_INODE_ACL
.get_inode_acl = scoutfs_get_acl,
#else
.get_acl = scoutfs_get_acl,
#ifdef KC_GET_ACL_DENTRY
#endif
#ifdef KC_SET_ACL_DENTRY
.set_acl = scoutfs_set_acl,
#endif
.fiemap = scoutfs_data_fiemap,
@@ -165,8 +169,12 @@ static const struct inode_operations scoutfs_special_iops = {
.removexattr = generic_removexattr,
#endif
.listxattr = scoutfs_listxattr,
#ifdef KC_GET_INODE_ACL
.get_inode_acl = scoutfs_get_acl,
#else
.get_acl = scoutfs_get_acl,
#ifdef KC_GET_ACL_DENTRY
#endif
#ifdef KC_SET_ACL_DENTRY
.set_acl = scoutfs_set_acl,
#endif
};