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fusefs: correctly handle an inode that changes file types

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Correctly handle the situation where a FUSE server unlinks a file, then
creates a new file of a different type but with the same inode number.
Previously fuse_vnop_lookup in this situation would return EAGAIN.  But
since it didn't call vgone(), the vnode couldn't be reused right away.
Fix this by immediately calling vgone() and reallocating a new vnode.

This problem can occur in three code paths, during VOP_LOOKUP,
VOP_SETATTR, or following FUSE_GETATTR, which usually happens during
VOP_GETATTR but can occur during other vops, too.  Note that the correct
response actually doesn't depend on whether the entry cache has expired.
In fact, during VOP_LOOKUP, we can't even tell.  Either it has expired
already, or else the vnode got reclaimed by vnlru.

Also, correct the error code during the VOP_SETATTR path.

PR:		258022
Reported by:	chogata@moosefs.pro
MFC after:	2 weeks
Reviewed by:	pfg
Differential Revision: https://reviews.freebsd.org/D33283
This commit is contained in:
Alan Somers 2021-12-05 22:43:17 -07:00
parent 169b368a62
commit 25927e068f
5 changed files with 142 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
sys/fs/fuse/fuse_internal.c
View File

@ -1255,12 +1255,15 @@ int fuse_internal_setattr(struct vnode *vp, struct vattr *vap,
* STALE vnode, ditch
*
* The vnode has changed its type "behind our back".
* This probably means that the file got deleted and
* recreated on the server, with the same inode.
* There's nothing really we can do, so let us just
* force an internal revocation and tell the caller to
* try again, if interested.
* return ENOENT. After all, the entry must not have
* existed in the recent past. If the user tries
* again, it will work.
*/
fuse_internal_vnode_disappear(vp);
err = EAGAIN;
err = ENOENT;
}
}
if (err == 0) {

25
sys/fs/fuse/fuse_node.c
View File

@ -213,24 +213,27 @@ fuse_vnode_alloc(struct mount *mp,
return (err);
if (*vpp) {
if ((*vpp)->v_type != vtyp) {
if ((*vpp)->v_type == vtyp) {
/* Reuse a vnode that hasn't yet been reclaimed */
MPASS((*vpp)->v_data != NULL);
MPASS(VTOFUD(*vpp)->nid == nodeid);
SDT_PROBE2(fusefs, , node, trace, 1,
"vnode taken from hash");
return (0);
} else {
/*
* STALE vnode! This probably indicates a buggy
* server, but it could also be the result of a race
* between FUSE_LOOKUP and another client's
* FUSE_UNLINK/FUSE_CREATE
* The inode changed types! If we get here, we can't
* tell whether the inode's entry cache had expired
* yet. So this could be the result of a buggy server,
* but more likely the server just reused an inode
* number following an entry cache expiration.
*/
SDT_PROBE3(fusefs, , node, stale_vnode, *vpp, vtyp,
nodeid);
fuse_internal_vnode_disappear(*vpp);
vgone(*vpp);
lockmgr((*vpp)->v_vnlock, LK_RELEASE, NULL);
*vpp = NULL;
return (EAGAIN);
}
MPASS((*vpp)->v_data != NULL);
MPASS(VTOFUD(*vpp)->nid == nodeid);
SDT_PROBE2(fusefs, , node, trace, 1, "vnode taken from hash");
return (0);
}
fvdat = malloc(sizeof(*fvdat), M_FUSEVN, M_WAITOK | M_ZERO);
switch (vtyp) {

50
tests/sys/fs/fusefs/getattr.cc
View File

@ -256,6 +256,56 @@ TEST_F(Getattr, ok)
//FUSE can't set st_blksize until protocol 7.9
}
/*
* FUSE_GETATTR returns a different file type, even though the entry cache
* hasn't expired. This is a server bug! It probably means that the server
* removed the file and recreated it with the same inode but a different vtyp.
* The best thing fusefs can do is return ENOENT to the caller. After all, the
* entry must not have existed recently.
*/
TEST_F(Getattr, vtyp_conflict)
{
const char FULLPATH[] = "mountpoint/some_file.txt";
const char RELPATH[] = "some_file.txt";
const uint64_t ino = 42;
struct stat sb;
sem_t sem;
ASSERT_EQ(0, sem_init(&sem, 0, 0)) << strerror(errno);
EXPECT_LOOKUP(FUSE_ROOT_ID, RELPATH)
.WillOnce(Invoke(
ReturnImmediate([=](auto in __unused, auto& out) {
SET_OUT_HEADER_LEN(out, entry);
out.body.entry.attr.mode = S_IFREG | 0644;
out.body.entry.nodeid = ino;
out.body.entry.attr.nlink = 1;
out.body.entry.attr_valid = 0;
out.body.entry.entry_valid = UINT64_MAX;
})));
EXPECT_CALL(*m_mock, process(
ResultOf([](auto in) {
return (in.header.opcode == FUSE_GETATTR &&
in.body.getattr.getattr_flags == 0 &&
in.header.nodeid == ino);
}, Eq(true)),
_)
).WillOnce(Invoke(ReturnImmediate([](auto i __unused, auto& out) {
SET_OUT_HEADER_LEN(out, attr);
out.body.attr.attr.ino = ino; // Must match nodeid
out.body.attr.attr.mode = S_IFDIR | 0755; // Changed!
out.body.attr.attr.nlink = 2;
})));
// We should reclaim stale vnodes
expect_forget(ino, 1, &sem);
ASSERT_NE(0, stat(FULLPATH, &sb));
EXPECT_EQ(errno, ENOENT);
sem_wait(&sem);
sem_destroy(&sem);
}
TEST_F(Getattr_7_8, ok)
{
const char FULLPATH[] = "mountpoint/some_file.txt";

30
tests/sys/fs/fusefs/lookup.cc
View File

@ -343,8 +343,9 @@ TEST_F(Lookup, subdir)
}
/*
* The server returns two different vtypes for the same nodeid. This is a bad
* server! But we shouldn't crash.
* The server returns two different vtypes for the same nodeid. This is
* technically allowed if the entry's cache has already expired.
* https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258022
*/
TEST_F(Lookup, vtype_conflict)
{
@ -354,12 +355,29 @@ TEST_F(Lookup, vtype_conflict)
const char SECONDRELPATH[] = "bar";
uint64_t ino = 42;
expect_lookup(FIRSTRELPATH, ino, S_IFREG | 0644, 0, 1, UINT64_MAX);
expect_lookup(SECONDRELPATH, ino, S_IFDIR | 0755, 0, 1, UINT64_MAX);
EXPECT_LOOKUP(FUSE_ROOT_ID, FIRSTRELPATH)
.WillOnce(Invoke(
ReturnImmediate([=](auto in __unused, auto& out) {
SET_OUT_HEADER_LEN(out, entry);
out.body.entry.attr.mode = S_IFDIR | 0644;
out.body.entry.nodeid = ino;
out.body.entry.attr.nlink = 1;
})));
expect_lookup(SECONDRELPATH, ino, S_IFREG | 0755, 0, 1, UINT64_MAX);
// VOP_FORGET happens asynchronously, so it may or may not arrive
// before the test completes.
EXPECT_CALL(*m_mock, process(
ResultOf([=](auto in) {
return (in.header.opcode == FUSE_FORGET &&
in.header.nodeid == ino &&
in.body.forget.nlookup == 1);
}, Eq(true)),
_)
).Times(AtMost(1))
.WillOnce(Invoke([=](auto in __unused, auto &out __unused) { }));
ASSERT_EQ(0, access(FIRSTFULLPATH, F_OK)) << strerror(errno);
ASSERT_EQ(-1, access(SECONDFULLPATH, F_OK));
ASSERT_EQ(EAGAIN, errno);
EXPECT_EQ(0, access(SECONDFULLPATH, F_OK)) << strerror(errno);
}
TEST_F(Lookup_7_8, ok)

47
tests/sys/fs/fusefs/setattr.cc
View File

@ -724,6 +724,53 @@ TEST_F(Setattr, utimensat_utime_now) {
EXPECT_EQ(now[1].tv_nsec, sb.st_mtim.tv_nsec);
}
/*
* FUSE_SETATTR returns a different file type, even though the entry cache
* hasn't expired. This is a server bug! It probably means that the server
* removed the file and recreated it with the same inode but a different vtyp.
* The best thing fusefs can do is return ENOENT to the caller. After all, the
* entry must not have existed recently.
*/
TEST_F(Setattr, vtyp_conflict)
{
const char FULLPATH[] = "mountpoint/some_file.txt";
const char RELPATH[] = "some_file.txt";
const uint64_t ino = 42;
uid_t newuser = 12345;
sem_t sem;
ASSERT_EQ(0, sem_init(&sem, 0, 0)) << strerror(errno);
EXPECT_LOOKUP(FUSE_ROOT_ID, RELPATH)
.WillOnce(Invoke(ReturnImmediate([=](auto in __unused, auto& out) {
SET_OUT_HEADER_LEN(out, entry);
out.body.entry.attr.mode = S_IFREG | 0777;
out.body.entry.nodeid = ino;
out.body.entry.entry_valid = UINT64_MAX;
})));
EXPECT_CALL(*m_mock, process(
ResultOf([](auto in) {
return (in.header.opcode == FUSE_SETATTR &&
in.header.nodeid == ino);
}, 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_IFDIR | 0777; // Changed!
out.body.attr.attr.uid = newuser;
})));
// We should reclaim stale vnodes
expect_forget(ino, 1, &sem);
EXPECT_NE(0, chown(FULLPATH, newuser, -1));
EXPECT_EQ(ENOENT, errno);
sem_wait(&sem);
sem_destroy(&sem);
}
/* On a read-only mount, no attributes may be changed */
TEST_F(RofsSetattr, erofs)
{