FUSE protocol 7.4 added the ability to cache negative lookups (see PR 236226). FreeBSD's fuse(4) doesn't currently do this, but it still needs to correctly interpret a cacheable negative response as ENOENT. Currently, we do that correctly when nameiop == LOOKUP. However, when nameiop == CREATE or RENAME we fail. In that case, we return ENOENT when we should return EJUSTRETURN. The symptom is that trying to create a new file will fail with ENOENT.
A commit references this bug: Author: asomers Date: Mon Mar 4 22:07:35 UTC 2019 New revision: 344785 URL: https://svnweb.freebsd.org/changeset/base/344785 Log: fuse(4): add tests for CREATE, OPEN, READLINK, SETATTR and SYMLINK The new SETATTR tests deal with already-open files. PR: 235775 PR: 236231 Sponsored by: The FreeBSD Foundation Changes: projects/fuse2/tests/sys/fs/fuse/Makefile projects/fuse2/tests/sys/fs/fuse/create.cc projects/fuse2/tests/sys/fs/fuse/mockfs.hh projects/fuse2/tests/sys/fs/fuse/open.cc projects/fuse2/tests/sys/fs/fuse/readlink.cc projects/fuse2/tests/sys/fs/fuse/setattr.cc projects/fuse2/tests/sys/fs/fuse/symlink.cc
(In reply to Alan Somers from comment #0) > However, when nameiop == CREATE or RENAME we fail. In that case, we return > ENOENT when we should return EJUSTRETURN. Can you elaborate? I think this is only true if negative lookup caching is enabled; I don't think it is in head. You're referring to fuse_vnop_lookup -> if (fuse_lookup_cache_enable) { ... switch (err) { ... ENOENT: return err ... } }? > The symptom is that trying to create a new file will fail with ENOENT. I have not observed this; probably because negative cache entry is hardcoded off in head around line 816 in the same function.
The bug happens even if the kernel doesn't try to cache negative lookups. It's not a bug in the cacheing per se; it's a bug in how we handle a cacheable response from the server. Here's what happens: Normal case, nameiop == LOOKUP: * fuse_vnop_lookup sends a FUSE_LOOKUP request to the server and waits for the answer via fdisp_wait_answ at line 738 * fdisk_wait_answ returns ENOENT * err = ENOENT at line 807, and return * some userland syscall gets ENOENT Normal case, nameiop = CREATE: * fuse_vnop_lookup sends a FUSE_LOOKUP request to the server and waits for the answer via fdisp_wait_answ at line 738 * fdisk_wait_answ returns ENOENT * err = EJUSTRETURN at line 786, and return * openat or one of its subroutines proceeds to VOP_CREATE Cacheable negative entry case, nameiop == LOOKUP: * fuse_vnop_lookup sends a FUSE_LOOKUP request to the server and waits for the answer via fdisp_wait_answ at line 738 * fdisk_wait_answ returns 0 * Since fdi.answ_stat == 0, return lookup_err at line 758. It's the right return code, but for the wrong reason * some userland syscall gets ENOENT Cacheable negative entry case, nameiop == CREATE: * fuse_vnop_lookup sends a FUSE_LOOKUP request to the server and waits for the answer via fdisp_wait_answ at line 738 * fdisk_wait_answ returns 0 * Since fdi.answ_stat is 0, return lookup_err at line 758. Oh no! * openat returns ENOENT, obviously a bogus error code when O_CREAT is set I haven't tried yet, but setting fdi.answ_stat = ENOENT at line 748 would probably fix the problem.
Thanks! I didn't realize the distinction between fdisp_wait_answ()'s return value and fdi.answ_stat. It seems like a confusing interface — we should return either a messaging error (return value) OR 0, with fdi.answ_stat set appropriately. Re: the 3rd and 4th cases, is it really true that FUSE_LOOKUP is expected to return success when no entry was found? Thanks.
(In reply to Conrad Meyer from comment #4) Yes, if no entry is found and the filesystem uses negative cacheing, then the fuse_out_header.error gets set to 0. See fuse_lib_lookup in devel/fusefs-libs.
A commit references this bug: Author: asomers Date: Tue Mar 5 18:53:29 UTC 2019 New revision: 344812 URL: https://svnweb.freebsd.org/changeset/base/344812 Log: fuse(4): add tests for FUSE_MKDIR and FUSE_ACCESS PR: 236291 PR: 236231 Sponsored by: The FreeBSD Foundation Changes: projects/fuse2/tests/sys/fs/fuse/Makefile projects/fuse2/tests/sys/fs/fuse/access.cc projects/fuse2/tests/sys/fs/fuse/mkdir.cc projects/fuse2/tests/sys/fs/fuse/mockfs.hh
A commit references this bug: Author: asomers Date: Thu Mar 21 23:31:11 UTC 2019 New revision: 345399 URL: https://svnweb.freebsd.org/changeset/base/345399 Log: fusefs: correctly handle cacheable negative LOOKUP responses The FUSE protocol allows for LOOKUP to return a cacheable negative response, which means that the file doesn't exist and the kernel can cache its nonexistence. As of this commit fusefs doesn't cache the nonexistence, but it does correctly handle such responses. Prior to this commit attempting to create a file, even with O_CREAT would fail with ENOENT if the daemon returned a cacheable negative response. PR: 236231 Sponsored by: The FreeBSD Foundation Changes: projects/fuse2/sys/fs/fuse/fuse_vnops.c projects/fuse2/tests/sys/fs/fusefs/create.cc projects/fuse2/tests/sys/fs/fusefs/mkdir.cc projects/fuse2/tests/sys/fs/fusefs/rename.cc
This is complete on the fuse2 branch.
A commit references this bug: Author: asomers Date: Wed Aug 7 00:38:29 UTC 2019 New revision: 350665 URL: https://svnweb.freebsd.org/changeset/base/350665 Log: fusefs: merge from projects/fuse2 This commit imports the new fusefs driver. It raises the protocol level from 7.8 to 7.23, fixes many bugs, adds a test suite for the driver, and adds many new features. New features include: * Optional kernel-side permissions checks (-o default_permissions) * Implement VOP_MKNOD, VOP_BMAP, and VOP_ADVLOCK * Allow interrupting FUSE operations * Support named pipes and unix-domain sockets in fusefs file systems * Forward UTIME_NOW during utimensat(2) to the daemon * kqueue support for /dev/fuse * Allow updating mounts with "mount -u" * Allow exporting fusefs file systems over NFS * Server-initiated invalidation of the name cache or data cache * Respect RLIMIT_FSIZE * Try to support servers as old as protocol 7.4 Performance enhancements include: * Implement FUSE's FOPEN_KEEP_CACHE and FUSE_ASYNC_READ flags * Cache file attributes * Cache lookup entries, both positive and negative * Server-selectable cache modes: writethrough, writeback, or uncached * Write clustering * Readahead * Use counter(9) for statistical reporting PR: 199934 216391 233783 234581 235773 235774 235775 PR: 236226 236231 236236 236291 236329 236381 236405 PR: 236327 236466 236472 236473 236474 236530 236557 PR: 236560 236844 237052 237181 237588 238565 Reviewed by: bcr (man pages) Reviewed by: cem, ngie, rpokala, glebius, kib, bde, emaste (post-commit review on project branch) MFC after: 3 weeks Relnotes: yes Sponsored by: The FreeBSD Foundation Pull Request: https://reviews.freebsd.org/D21110 Changes: _U head/ head/MAINTAINERS head/UPDATING head/etc/mtree/BSD.tests.dist head/sbin/mount_fusefs/mount_fusefs.8 head/sbin/mount_fusefs/mount_fusefs.c head/share/man/man5/fusefs.5 head/sys/fs/fuse/fuse.h head/sys/fs/fuse/fuse_device.c head/sys/fs/fuse/fuse_file.c head/sys/fs/fuse/fuse_file.h head/sys/fs/fuse/fuse_internal.c head/sys/fs/fuse/fuse_internal.h head/sys/fs/fuse/fuse_io.c head/sys/fs/fuse/fuse_io.h head/sys/fs/fuse/fuse_ipc.c head/sys/fs/fuse/fuse_ipc.h head/sys/fs/fuse/fuse_kernel.h head/sys/fs/fuse/fuse_main.c head/sys/fs/fuse/fuse_node.c head/sys/fs/fuse/fuse_node.h head/sys/fs/fuse/fuse_param.h head/sys/fs/fuse/fuse_vfsops.c head/sys/fs/fuse/fuse_vnops.c head/sys/sys/param.h head/tests/sys/fs/Makefile head/tests/sys/fs/fusefs/
A commit references this bug: Author: asomers Date: Sun Sep 15 04:14:34 UTC 2019 New revision: 352351 URL: https://svnweb.freebsd.org/changeset/base/352351 Log: MFC the new fusefs driver MFC r350665, r350990, r350992, r351039, r351042, r351061, r351066, r351113, r351560, r351961, r351963, r352021, r352025, r352230 r350665: fusefs: merge from projects/fuse2 This commit imports the new fusefs driver. It raises the protocol level from 7.8 to 7.23, fixes many bugs, adds a test suite for the driver, and adds many new features. New features include: * Optional kernel-side permissions checks (-o default_permissions) * Implement VOP_MKNOD, VOP_BMAP, and VOP_ADVLOCK * Allow interrupting FUSE operations * Support named pipes and unix-domain sockets in fusefs file systems * Forward UTIME_NOW during utimensat(2) to the daemon * kqueue support for /dev/fuse * Allow updating mounts with "mount -u" * Allow exporting fusefs file systems over NFS * Server-initiated invalidation of the name cache or data cache * Respect RLIMIT_FSIZE * Try to support servers as old as protocol 7.4 Performance enhancements include: * Implement FUSE's FOPEN_KEEP_CACHE and FUSE_ASYNC_READ flags * Cache file attributes * Cache lookup entries, both positive and negative * Server-selectable cache modes: writethrough, writeback, or uncached * Write clustering * Readahead * Use counter(9) for statistical reporting PR: 199934 216391 233783 234581 235773 235774 235775 PR: 236226 236231 236236 236291 236329 236381 236405 PR: 236327 236466 236472 236473 236474 236530 236557 PR: 236560 236844 237052 237181 237588 238565 Reviewed by: bcr (man pages) Reviewed by: cem, ngie, rpokala, glebius, kib, bde, emaste (post-commit review on project branch) Relnotes: yes Sponsored by: The FreeBSD Foundation Pull Request: https://reviews.freebsd.org/D21110 r350990: fusefs: add SVN Keywords to the test files Reported by: SVN pre-commit hooks MFC-With: r350665 Sponsored by: The FreeBSD Foundation r350992: fusefs: skip some tests when unsafe aio is disabled MFC-With: r350665 Sponsored by: The FreeBSD Foundation r351039: fusefs: fix intermittency in the default_permissions.Unlink.ok test The test needs to expect a FUSE_FORGET operation. Most of the time the test would pass anyway, because by chance FUSE_FORGET would arrive after the unmount. MFC-With: 350665 Sponsored by: The FreeBSD Foundation r351042: fusefs: Fix the size of fuse_getattr_in In FUSE protocol 7.9, the size of the FUSE_GETATTR request has increased. However, the fusefs driver is currently not sending the additional fields. In our implementation, the additional fields are always zero, so I there haven't been any test failures until now. But fusefs-lkl requires the request's length to be correct. Fix this bug, and also enhance the test suite to catch similar bugs. PR: 239830 MFC-With: 350665 Sponsored by: The FreeBSD Foundation r351061: fusefs: fix the 32-bit build after 351042 Reported by: jhb MFC-With: 351042 Sponsored by: The FreeBSD Foundation r351066: fusefs: fix conditional from r351061 The entirety of r351061 was a copy/paste error. I'm sorry I've been comitting so hastily. Reported by: rpokala Reviewed by: rpokala MFC-With: 351061 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21265 r351113: fusefs: don't send the namespace during listextattr The FUSE_LISTXATTR operation always returns the full list of a file's extended attributes, in all namespaces. There's no way to filter the list server-side. However, currently FreeBSD's fusefs driver sends a namespace string with the FUSE_LISTXATTR request. That behavior was probably copied from fuse_vnop_getextattr, which has an attribute name argument. It's been there ever since extended attribute support was added in r324620. This commit removes it. Reviewed by: cem Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21280 r351560: fusefs: Fix some bugs regarding the size of the LISTXATTR list * A small error in r338152 let to the returned size always being exactly eight bytes too large. * The FUSE_LISTXATTR operation works like Linux's listxattr(2): if the caller does not provide enough space, then the server should return ERANGE rather than return a truncated list. That's true even though in FUSE's case the kernel doesn't provide space to the client at all; it simply requests a maximum size for the list. We previously weren't handling the case where the server returns ERANGE even though the kernel requested as much size as the server had told us it needs; that can happen due to a race. * We also need to ensure that a pathological server that always returns ERANGE no matter what size we request in FUSE_LISTXATTR won't cause an infinite loop in the kernel. As of this commit, it will instead cause an infinite loop that exits and enters the kernel on each iteration, allowing signals to be processed. Reviewed by: cem Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21287 r351961: Coverity fixes in fusefs(5) CID 1404532 fixes a signed vs unsigned comparison error in fuse_vnop_bmap. It could potentially have resulted in VOP_BMAP reporting too many consecutive blocks. CID 1404364 is much worse. It was an array access by an untrusted, user-provided variable. It could potentially have resulted in a malicious file system crashing the kernel or worse. Reported by: Coverity Reviewed by: emaste Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21466 r351963: fusefs: coverity cleanup in the tests Address the following defects reported by Coverity: * Structurally dead code (CID 1404366): set m_quit before FAIL, not after * Unchecked return value of sysctlbyname (CID 1404321) * Unchecked return value of stat(2) (CID 1404471) * Unchecked return value of open(2) (CID 1404402, 1404529) * Unchecked return value of dup(2) (CID 1404478) * Buffer overflows. These are all false positives caused by the fact that Coverity thinks I'm using a buffer to store strings, when in fact I'm really just using it to store a byte array that happens to be initialized with a string. I'm changing the type from char to uint8_t in the hopes that it will placate Coverity. (CID 1404338, 1404350, 1404367, 1404376, 1404379, 1404381, 1404388, 1404403, 1404425, 1404433, 1404434, 1404474, 1404480, 1404484, 1404503, 1404505) * False positive file descriptor leak. I'm going to try to fix this with Coverity modeling, but I'll also change an EXPECT to ASSERT so we don't perform meaningless assertions after the failure. (CID 1404320, 1404324, 1404440, 1404445). * Unannotated file descriptor leak. This will be followed up by a Coverity modeling change. (CID 1404326, 1404334, 1404336, 1404357, 1404361, 1404372, 1404391, 1404395, 1404409, 1404430, 1404448, 1404451, 1404455, 1404457, 1404458, 1404460) * Uninitialized variables in C++ constructors (CID 1404327, 1404346). In the case of m_maxphys, this actually led to part of the FUSE_INIT's response being set to stack garbage during the WriteCluster::clustering test. * Uninitialized sun_len field in struct sockaddr_un (CID 1404330, 1404371, 1404429). Reported by: Coverity Reviewed by: emaste Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21457 r352021: fusefs: suppress some Coverity resource leak CIDs in the tests The fusefs tests deliberately leak file descriptors. To do otherwise would add extra complications to the tests' mock FUSE server. This annotation should hopefully convince Coverity to shut up about the leaks. Reviewed by: uqs Sponsored by: The FreeBSD Foundation r352025: mount_fusefs: fix a segfault on memory allocation failure Reported by: Coverity Coverity CID: 1354188 Sponsored by: The FreeBSD Foundation r352230: fusefs: Fix iosize for FUSE_WRITE in 7.8 compat mode When communicating with a FUSE server that implements version 7.8 (or older) of the FUSE protocol, the FUSE_WRITE request structure is 16 bytes shorter than normal. The protocol version check wasn't applied universally, leading to an extra 16 bytes being sent to such servers. The extra bytes were allocated and bzero()d, so there was no information disclosure. Reviewed by: emaste MFC-With: r350665 Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D21557 Changes: _U stable/12/ stable/12/MAINTAINERS stable/12/UPDATING stable/12/etc/mtree/BSD.tests.dist stable/12/sbin/mount_fusefs/mount_fusefs.8 stable/12/sbin/mount_fusefs/mount_fusefs.c stable/12/share/man/man5/fusefs.5 stable/12/sys/fs/fuse/fuse.h stable/12/sys/fs/fuse/fuse_device.c stable/12/sys/fs/fuse/fuse_file.c stable/12/sys/fs/fuse/fuse_file.h stable/12/sys/fs/fuse/fuse_internal.c stable/12/sys/fs/fuse/fuse_internal.h stable/12/sys/fs/fuse/fuse_io.c stable/12/sys/fs/fuse/fuse_io.h stable/12/sys/fs/fuse/fuse_ipc.c stable/12/sys/fs/fuse/fuse_ipc.h stable/12/sys/fs/fuse/fuse_kernel.h stable/12/sys/fs/fuse/fuse_main.c stable/12/sys/fs/fuse/fuse_node.c stable/12/sys/fs/fuse/fuse_node.h stable/12/sys/fs/fuse/fuse_param.h stable/12/sys/fs/fuse/fuse_vfsops.c stable/12/sys/fs/fuse/fuse_vnops.c stable/12/sys/sys/param.h stable/12/tests/sys/fs/Makefile stable/12/tests/sys/fs/fusefs/ stable/12/tests/sys/fs/fusefs/access.cc stable/12/tests/sys/fs/fusefs/allow_other.cc stable/12/tests/sys/fs/fusefs/bmap.cc stable/12/tests/sys/fs/fusefs/create.cc stable/12/tests/sys/fs/fusefs/default_permissions.cc stable/12/tests/sys/fs/fusefs/default_permissions_privileged.cc stable/12/tests/sys/fs/fusefs/destroy.cc stable/12/tests/sys/fs/fusefs/dev_fuse_poll.cc stable/12/tests/sys/fs/fusefs/fifo.cc stable/12/tests/sys/fs/fusefs/flush.cc stable/12/tests/sys/fs/fusefs/forget.cc stable/12/tests/sys/fs/fusefs/fsync.cc stable/12/tests/sys/fs/fusefs/fsyncdir.cc stable/12/tests/sys/fs/fusefs/getattr.cc stable/12/tests/sys/fs/fusefs/interrupt.cc stable/12/tests/sys/fs/fusefs/io.cc stable/12/tests/sys/fs/fusefs/link.cc stable/12/tests/sys/fs/fusefs/locks.cc stable/12/tests/sys/fs/fusefs/lookup.cc stable/12/tests/sys/fs/fusefs/mkdir.cc stable/12/tests/sys/fs/fusefs/mknod.cc stable/12/tests/sys/fs/fusefs/mockfs.cc stable/12/tests/sys/fs/fusefs/mockfs.hh stable/12/tests/sys/fs/fusefs/mount.cc stable/12/tests/sys/fs/fusefs/nfs.cc stable/12/tests/sys/fs/fusefs/notify.cc stable/12/tests/sys/fs/fusefs/open.cc stable/12/tests/sys/fs/fusefs/opendir.cc stable/12/tests/sys/fs/fusefs/read.cc stable/12/tests/sys/fs/fusefs/readdir.cc stable/12/tests/sys/fs/fusefs/readlink.cc stable/12/tests/sys/fs/fusefs/release.cc stable/12/tests/sys/fs/fusefs/releasedir.cc stable/12/tests/sys/fs/fusefs/rename.cc stable/12/tests/sys/fs/fusefs/rmdir.cc stable/12/tests/sys/fs/fusefs/setattr.cc stable/12/tests/sys/fs/fusefs/statfs.cc stable/12/tests/sys/fs/fusefs/symlink.cc stable/12/tests/sys/fs/fusefs/unlink.cc stable/12/tests/sys/fs/fusefs/utils.cc stable/12/tests/sys/fs/fusefs/utils.hh stable/12/tests/sys/fs/fusefs/write.cc stable/12/tests/sys/fs/fusefs/xattr.cc