Allow changing the file mode, UID, and GID through SETATTR.
Without allow_other, UID and GID are not allowed to be changed, because
it would not make sense. Also, changing group or others' permissions
is not allowed either.
For read-only exports, +w cannot be set.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
block/export/fuse.c | 73 ++++++++++++++++++++++++++++++++++++++-------
1 file changed, 62 insertions(+), 11 deletions(-)
diff --git a/block/export/fuse.c b/block/export/fuse.c
index 26ad644cd7..ada9e263eb 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -48,6 +48,10 @@ typedef struct FuseExport {
bool growable;
/* Whether allow_other was used as a mount option or not */
bool allow_other;
+
+ mode_t st_mode;
+ uid_t st_uid;
+ gid_t st_gid;
} FuseExport;
static GHashTable *exports;
@@ -125,6 +129,13 @@ static int fuse_export_create(BlockExport *blk_exp,
args->allow_other = FUSE_EXPORT_ALLOW_OTHER_AUTO;
}
+ exp->st_mode = S_IFREG | S_IRUSR;
+ if (exp->writable) {
+ exp->st_mode |= S_IWUSR;
+ }
+ exp->st_uid = getuid();
+ exp->st_gid = getgid();
+
if (args->allow_other == FUSE_EXPORT_ALLOW_OTHER_AUTO) {
/* Ignore errors on our first attempt */
ret = setup_fuse_export(exp, args->mountpoint, true, NULL);
@@ -338,7 +349,6 @@ static void fuse_getattr(fuse_req_t req, fuse_ino_t inode,
int64_t length, allocated_blocks;
time_t now = time(NULL);
FuseExport *exp = fuse_req_userdata(req);
- mode_t mode;
length = blk_getlength(exp->common.blk);
if (length < 0) {
@@ -353,17 +363,12 @@ static void fuse_getattr(fuse_req_t req, fuse_ino_t inode,
allocated_blocks = DIV_ROUND_UP(allocated_blocks, 512);
}
- mode = S_IFREG | S_IRUSR;
- if (exp->writable) {
- mode |= S_IWUSR;
- }
-
statbuf = (struct stat) {
.st_ino = inode,
- .st_mode = mode,
+ .st_mode = exp->st_mode,
.st_nlink = 1,
- .st_uid = getuid(),
- .st_gid = getgid(),
+ .st_uid = exp->st_uid,
+ .st_gid = exp->st_gid,
.st_size = length,
.st_blksize = blk_bs(exp->common.blk)->bl.request_alignment,
.st_blocks = allocated_blocks,
@@ -409,19 +414,52 @@ static int fuse_do_truncate(const FuseExport *exp,
int64_t size,
}
/**
- * Let clients set file attributes. Only resizing is supported.
+ * Let clients set file attributes. Only resizing and changing
+ * permissions (st_mode, st_uid, st_gid) is allowed.
+ * Changing permissions is only allowed as far as it will actually
+ * permit access: Read-only exports cannot be given +w, and exports
+ * without allow_other cannot be given a different UID or GID, and
+ * they cannot be given non-owner access.
*/
static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat
*statbuf,
int to_set, struct fuse_file_info *fi)
{
FuseExport *exp = fuse_req_userdata(req);
+ int supported_attrs;
int ret;
- if (to_set & ~FUSE_SET_ATTR_SIZE) {
+ supported_attrs = FUSE_SET_ATTR_SIZE | FUSE_SET_ATTR_MODE;
+ if (exp->allow_other) {
+ supported_attrs |= FUSE_SET_ATTR_UID | FUSE_SET_ATTR_GID;
+ }
+
+ if (to_set & ~supported_attrs) {
fuse_reply_err(req, ENOTSUP);
return;
}
+ /* Do some argument checks first before committing to anything */
+ if (to_set & FUSE_SET_ATTR_MODE) {
+ /*
+ * Without allow_other, non-owners can never access the export, so do
+ * not allow setting permissions for them
+ */
+ if (!exp->allow_other &&
+ (statbuf->st_mode & (S_IRWXG | S_IRWXO)) != 0)
+ {
+ fuse_reply_err(req, EPERM);
+ return;
+ }
+
+ /* +w for read-only exports makes no sense, disallow it */
+ if (!exp->writable &&
+ (statbuf->st_mode & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
+ {
+ fuse_reply_err(req, EROFS);
+ return;
+ }
+ }
+
if (to_set & FUSE_SET_ATTR_SIZE) {
if (!exp->writable) {
fuse_reply_err(req, EACCES);
@@ -435,6 +473,19 @@ static void fuse_setattr(fuse_req_t req, fuse_ino_t inode,
struct stat *statbuf,
}
}
+ if (to_set & FUSE_SET_ATTR_MODE) {
+ /* Ignore FUSE-supplied file type, only change the mode */
+ exp->st_mode = (statbuf->st_mode & 07777) | S_IFREG;
+ }
+
+ if (to_set & FUSE_SET_ATTR_UID) {
+ exp->st_uid = statbuf->st_uid;
+ }
+
+ if (to_set & FUSE_SET_ATTR_GID) {
+ exp->st_gid = statbuf->st_gid;
+ }
+
fuse_getattr(req, inode, fi);
}
--
2.31.1
