[PATCH v2 1/2] fuse: Add support for FUSE_SETXATTR_V2

From: Vivek Goyal
Date: Thu Mar 25 2021 - 11:19:40 EST


Fuse client needs to send additional information to file server when
it calls SETXATTR(system.posix_acl_access). Right now there is no extra
space in fuse_setxattr_in. So introduce a v2 of the structure which has
more space in it and can be used to send extra flags.

"struct fuse_setxattr_in_v2" is only used if file server opts-in for it using
flag FUSE_SETXATTR_V2 during feature negotiations.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/fuse/acl.c | 2 +-
fs/fuse/fuse_i.h | 5 ++++-
fs/fuse/inode.c | 4 +++-
fs/fuse/xattr.c | 21 +++++++++++++++------
include/uapi/linux/fuse.h | 10 ++++++++++
5 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index e9c0f916349d..d31260a139d4 100644
--- a/fs/fuse/acl.c
+++ b/fs/fuse/acl.c
@@ -94,7 +94,7 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
return ret;
}

- ret = fuse_setxattr(inode, name, value, size, 0);
+ ret = fuse_setxattr(inode, name, value, size, 0, 0);
kfree(value);
} else {
ret = fuse_removexattr(inode, name);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 63d97a15ffde..d00bf0b9a38c 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -668,6 +668,9 @@ struct fuse_conn {
/** Is setxattr not implemented by fs? */
unsigned no_setxattr:1;

+ /** Does file server support setxattr_v2 */
+ unsigned setxattr_v2:1;
+
/** Is getxattr not implemented by fs? */
unsigned no_getxattr:1;

@@ -1170,7 +1173,7 @@ void fuse_unlock_inode(struct inode *inode, bool locked);
bool fuse_lock_inode(struct inode *inode);

int fuse_setxattr(struct inode *inode, const char *name, const void *value,
- size_t size, int flags);
+ size_t size, int flags, unsigned extra_flags);
ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
size_t size);
ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index b0e18b470e91..1c726df13f80 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1052,6 +1052,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
fc->handle_killpriv_v2 = 1;
fm->sb->s_flags |= SB_NOSEC;
}
+ if (arg->flags & FUSE_SETXATTR_V2)
+ fc->setxattr_v2 = 1;
} else {
ra_pages = fc->max_read / PAGE_SIZE;
fc->no_lock = 1;
@@ -1095,7 +1097,7 @@ void fuse_send_init(struct fuse_mount *fm)
FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
- FUSE_HANDLE_KILLPRIV_V2;
+ FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_V2;
#ifdef CONFIG_FUSE_DAX
if (fm->fc->dax)
ia->in.flags |= FUSE_MAP_ALIGNMENT;
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index 1a7d7ace54e1..f2aae72653dc 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -12,24 +12,33 @@
#include <linux/posix_acl_xattr.h>

int fuse_setxattr(struct inode *inode, const char *name, const void *value,
- size_t size, int flags)
+ size_t size, int flags, unsigned extra_flags)
{
struct fuse_mount *fm = get_fuse_mount(inode);
FUSE_ARGS(args);
struct fuse_setxattr_in inarg;
+ struct fuse_setxattr_in_v2 inarg_v2;
+ bool setxattr_v2 = fm->fc->setxattr_v2;
int err;

if (fm->fc->no_setxattr)
return -EOPNOTSUPP;

memset(&inarg, 0, sizeof(inarg));
- inarg.size = size;
- inarg.flags = flags;
+ memset(&inarg_v2, 0, sizeof(inarg_v2));
+ if (setxattr_v2) {
+ inarg_v2.size = size;
+ inarg_v2.flags = flags;
+ inarg_v2.setxattr_flags = extra_flags;
+ } else {
+ inarg.size = size;
+ inarg.flags = flags;
+ }
args.opcode = FUSE_SETXATTR;
args.nodeid = get_node_id(inode);
args.in_numargs = 3;
- args.in_args[0].size = sizeof(inarg);
- args.in_args[0].value = &inarg;
+ args.in_args[0].size = setxattr_v2 ? sizeof(inarg_v2) : sizeof(inarg);
+ args.in_args[0].value = setxattr_v2 ? &inarg_v2 : (void *)&inarg;
args.in_args[1].size = strlen(name) + 1;
args.in_args[1].value = name;
args.in_args[2].size = size;
@@ -199,7 +208,7 @@ static int fuse_xattr_set(const struct xattr_handler *handler,
if (!value)
return fuse_removexattr(inode, name);

- return fuse_setxattr(inode, name, value, size, flags);
+ return fuse_setxattr(inode, name, value, size, flags, 0);
}

static bool no_xattr_list(struct dentry *dentry)
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 54442612c48b..1bb555c1c117 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -179,6 +179,7 @@
* 7.33
* - add FUSE_HANDLE_KILLPRIV_V2, FUSE_WRITE_KILL_SUIDGID, FATTR_KILL_SUIDGID
* - add FUSE_OPEN_KILL_SUIDGID
+ * - add FUSE_SETXATTR_V2
*/

#ifndef _LINUX_FUSE_H
@@ -330,6 +331,7 @@ struct fuse_file_lock {
* does not have CAP_FSETID. Additionally upon
* write/truncate sgid is killed only if file has group
* execute permission. (Same as Linux VFS behavior).
+ * FUSE_SETXATTR_V2: Does file server support V2 of struct fuse_setxattr_in
*/
#define FUSE_ASYNC_READ (1 << 0)
#define FUSE_POSIX_LOCKS (1 << 1)
@@ -360,6 +362,7 @@ struct fuse_file_lock {
#define FUSE_MAP_ALIGNMENT (1 << 26)
#define FUSE_SUBMOUNTS (1 << 27)
#define FUSE_HANDLE_KILLPRIV_V2 (1 << 28)
+#define FUSE_SETXATTR_V2 (1 << 29)

/**
* CUSE INIT request/reply flags
@@ -686,6 +689,13 @@ struct fuse_setxattr_in {
uint32_t flags;
};

+struct fuse_setxattr_in_v2 {
+ uint32_t size;
+ uint32_t flags;
+ uint32_t setxattr_flags;
+ uint32_t padding;
+};
+
struct fuse_getxattr_in {
uint32_t size;
uint32_t padding;
--
2.25.4