From: Vivek Goyal vgoyal@redhat.com
mainline inclusion from mainline-v5.11-rc1 commit 63f9909ff602082597849f684655e93336c50b11 category: perf bugzilla: https://gitee.com/openeuler/kernel/issues/I4SIR8
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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We already have FUSE_HANDLE_KILLPRIV flag that says that file server will remove suid/sgid/caps on truncate/chown/write. But that's little different from what Linux VFS implements.
To be consistent with Linux VFS behavior what we want is.
- caps are always cleared on chown/write/truncate - suid is always cleared on chown, while for truncate/write it is cleared only if caller does not have CAP_FSETID. - sgid is always cleared on chown, while for truncate/write it is cleared only if caller does not have CAP_FSETID as well as file has group execute permission.
As previous flag did not provide above semantics. Implement a V2 of the protocol with above said constraints.
Server does not know if caller has CAP_FSETID or not. So for the case of write()/truncate(), client will send information in special flag to indicate whether to kill priviliges or not. These changes are in subsequent patches.
FUSE_HANDLE_KILLPRIV_V2 relies on WRITE being sent to server to clear suid/sgid/security.capability. But with ->writeback_cache, WRITES are cached in guest. So it is not recommended to use FUSE_HANDLE_KILLPRIV_V2 and writeback_cache together. Though it probably might be good enough for lot of use cases.
Signed-off-by: Vivek Goyal vgoyal@redhat.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/fuse/fuse_i.h | 8 ++++++++ fs/fuse/inode.c | 5 ++++- include/uapi/linux/fuse.h | 11 ++++++++++- 3 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index ed71ef6fbc9d..d31fc48c6afa 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -642,6 +642,14 @@ struct fuse_conn { /* show legacy mount options */ unsigned int legacy_opts_show:1;
+ /* + * fs kills suid/sgid/cap on write/chown/trunc. suid is killed on + * write/trunc only if caller did not have CAP_FSETID. sgid is killed + * on write/truncate only if caller did not have CAP_FSETID as well as + * file has group execute permission. + */ + unsigned handle_killpriv_v2:1; + /* * The following bitfields are only for optimization purposes * and hence races in setting them will not cause malfunction diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 5e484676343e..59765df54fa7 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1058,6 +1058,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, !fuse_dax_check_alignment(fc, arg->map_alignment)) { ok = false; } + if (arg->flags & FUSE_HANDLE_KILLPRIV_V2) + fc->handle_killpriv_v2 = 1; } else { ra_pages = fc->max_read / PAGE_SIZE; fc->no_lock = 1; @@ -1100,7 +1102,8 @@ void fuse_send_init(struct fuse_mount *fm) FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT | 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_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA | + FUSE_HANDLE_KILLPRIV_V2; #ifdef CONFIG_FUSE_DAX if (fm->fc->dax) ia->in.flags |= FUSE_MAP_ALIGNMENT; diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 7233502ea991..29bd2e007947 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -175,6 +175,9 @@ * * 7.32 * - add flags to fuse_attr, add FUSE_ATTR_SUBMOUNT, add FUSE_SUBMOUNTS + * + * 7.33 + * - add FUSE_HANDLE_KILLPRIV_V2 */
#ifndef _LINUX_FUSE_H @@ -210,7 +213,7 @@ #define FUSE_KERNEL_VERSION 7
/** Minor version number of this interface */ -#define FUSE_KERNEL_MINOR_VERSION 32 +#define FUSE_KERNEL_MINOR_VERSION 33
/** The node ID of the root inode */ #define FUSE_ROOT_ID 1 @@ -320,6 +323,11 @@ struct fuse_file_lock { * foffset and moffset fields in struct * fuse_setupmapping_out and fuse_removemapping_one. * FUSE_SUBMOUNTS: kernel supports auto-mounting directory submounts + * FUSE_HANDLE_KILLPRIV_V2: fs kills suid/sgid/cap on write/chown/trunc. + * Upon write/truncate suid/sgid is only killed if caller + * does not have CAP_FSETID. Additionally upon + * write/truncate sgid is killed only if file has group + * execute permission. (Same as Linux VFS behavior). */ #define FUSE_ASYNC_READ (1 << 0) #define FUSE_POSIX_LOCKS (1 << 1) @@ -349,6 +357,7 @@ struct fuse_file_lock { #define FUSE_EXPLICIT_INVAL_DATA (1 << 25) #define FUSE_MAP_ALIGNMENT (1 << 26) #define FUSE_SUBMOUNTS (1 << 27) +#define FUSE_HANDLE_KILLPRIV_V2 (1 << 28)
/** * CUSE INIT request/reply flags