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fusefs: allow ftruncate on files without write permission

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ftruncate should succeed as long as the file descriptor is writable, even if
the file doesn't have write permission.  This is important when combined
with O_CREAT.

Reported by:	pjdfstest
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
asomers 2019-05-06 20:46:58 +00:00
parent d4fb8d71ef
commit 2da486ebf1
3 changed files with 60 additions and 24 deletions
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3
sys/fs/fuse/fuse_internal.c
View File

@ -128,6 +128,9 @@ fuse_internal_access(struct vnode *vp,
data = fuse_get_mpdata(mp);
dataflags = data->dataflags;
if (mode == 0)
return 0;
if (mode & VMODIFY_PERMS && vfs_isrdonly(mp)) {
switch (vp->v_type) {
case VDIR:

2
sys/fs/fuse/fuse_vnops.c
View File

@ -1574,7 +1574,7 @@ fuse_vnop_setattr(struct vop_setattr_args *ap)
*/
return (0);
}
accmode |= VWRITE;
/* Don't set accmode. Permission to trunc is checked upstack */
}
/*
* TODO: for atime and mtime, only require VWRITE if UTIMENS_NULL is

79
tests/sys/fs/fusefs/default_permissions.cc
View File

@ -86,6 +86,25 @@ void expect_chmod(uint64_t ino, mode_t mode)
})));
}
void expect_create(const char *relpath, uint64_t ino)
{
EXPECT_CALL(*m_mock, process(
ResultOf([=](auto in) {
const char *name = (const char*)in->body.bytes +
sizeof(fuse_open_in);
return (in->header.opcode == FUSE_CREATE &&
(0 == strcmp(relpath, name)));
}, Eq(true)),
_)
).WillOnce(Invoke(ReturnImmediate([=](auto in __unused, auto out) {
SET_OUT_HEADER_LEN(out, create);
out->body.create.entry.attr.mode = S_IFREG | 0644;
out->body.create.entry.nodeid = ino;
out->body.create.entry.entry_valid = UINT64_MAX;
out->body.create.entry.attr_valid = UINT64_MAX;
})));
}
void expect_getattr(uint64_t ino, mode_t mode, uint64_t attr_valid, int times,
uid_t uid = 0, gid_t gid = 0)
{
@ -129,29 +148,7 @@ class Write: public DefaultPermissions {};
* rename vops (they all share a common path for permission checks in
* VOP_LOOKUP)
*/
class Create: public DefaultPermissions {
public:
void expect_create(const char *relpath, uint64_t ino)
{
EXPECT_CALL(*m_mock, process(
ResultOf([=](auto in) {
const char *name = (const char*)in->body.bytes +
sizeof(fuse_open_in);
return (in->header.opcode == FUSE_CREATE &&
(0 == strcmp(relpath, name)));
}, Eq(true)),
_)
).WillOnce(Invoke(ReturnImmediate([=](auto in __unused, auto out) {
SET_OUT_HEADER_LEN(out, create);
out->body.create.entry.attr.mode = S_IFREG | 0644;
out->body.create.entry.nodeid = ino;
out->body.create.entry.entry_valid = UINT64_MAX;
out->body.create.entry.attr_valid = UINT64_MAX;
})));
}
};
class Create: public DefaultPermissions {};
class Deleteextattr: public DefaultPermissions {
public:
@ -797,6 +794,42 @@ TEST_F(Setattr, eacces)
EXPECT_EQ(EPERM, errno);
}
/*
* ftruncate() of a file without writable permissions should succeed as long as
* the file descriptor is writable. This is important when combined with
* O_CREAT
*/
TEST_F(Setattr, ftruncate_of_newly_created_file)
{
const char FULLPATH[] = "mountpoint/some_file.txt";
const char RELPATH[] = "some_file.txt";
const uint64_t ino = 42;
const mode_t mode = 0000;
int fd;
expect_getattr(1, S_IFDIR | 0777, UINT64_MAX, 1);
EXPECT_LOOKUP(1, RELPATH).WillOnce(Invoke(ReturnErrno(ENOENT)));
expect_create(RELPATH, ino);
EXPECT_CALL(*m_mock, process(
ResultOf([](auto in) {
return (in->header.opcode == FUSE_SETATTR &&
in->header.nodeid == ino &&
(in->body.setattr.valid & FATTR_SIZE));
}, Eq(true)),
_)
).WillOnce(Invoke(ReturnImmediate([=](auto in __unused, auto out) {
SET_OUT_HEADER_LEN(out, attr);
out->body.attr.attr.ino = ino;
out->body.attr.attr.mode = S_IFREG | mode;
out->body.attr.attr_valid = UINT64_MAX;
})));
fd = open(FULLPATH, O_CREAT | O_RDWR, 0);
ASSERT_LE(0, fd) << strerror(errno);
ASSERT_EQ(0, ftruncate(fd, 100)) << strerror(errno);
/* Deliberately leak fd */
}
/*
* Setting the sgid bit should fail for an unprivileged user who doesn't belong
* to the file's group