Both FreeBSD and Linux mkdir -p walk the tree up ignoring any EEXIST on
the way and both are used a lot when building respective kernels.
This poses a problem as spurious locking avoidably interferes with
concurrent operations like getdirentries on affected directories.
Work around the problem by adding FAILIFEXISTS flag. In case of lockless
lookup this manages to avoid any work to begin with, there is no speed
up for the locked case but perhaps this can be augmented later on.
For simplicity the only supported semantics are as used by mkdir.
Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D27789
struct nameidata mixes caller arguments, internal state and output, which
can be quite error prone.
Recent addition of valdiating ni_resflags uncovered a caller which could
repeatedly call namei, effectively operating on partially populated state.
Add bare minimium validation this does not happen. The real fix would
decouple aforementioned state.
Reported by: pho
Tested by: pho (different variant)
Specifically, if lookup() returned any error and the topping directory
was not latched, which means that (non-existent) path did not returned
to the topping location, give ENOTCAPABLE a priority over the lookup()
error.
PR: 249960
Reviewed by: emaste, ngie
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D26695
It is like O_BENEATH, but disables to walk out of the subtree rooted
in the starting directory. O_BENEATH does not care if path walks out
if it returned.
Requested by: Dan Gohman <dev@sunfishcode.online>
PR: 248335
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
Do not care if path walks out of the topping directory if it returns back.
Requested and reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
not unconditionally on any dotdot component.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
Stop abusing internal namei flag NI_LCF_STRICTRELATIVE as indicator of
cap-restricted lookup. Add designated returned flag NIRES_STRICTREL
to inform kern_openat() that lookup was restricted.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
This makes open("/a/../a", O_BENEATH) with cwd == "/a" work.
Reviewed by: markj
Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
Explain why tracker is needed at all.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
While here change the field size from long to int and move it into the
gap next to cn_flags.
Shrinks struct componentname from 64 to 56 bytes on amd64.
The actual bug is not yet addressed as it will get much easier after other
problems are addressed (most notably rename contract).
The only affected in-tree consumer is realpath. Everyone else happens to be
performing lookups within a mount point, having a side effect of ni_dvp being
set to mount point's root vnode in the worst case.
Reported by: pho
namei de facto expects that the naimeidata object is properly initialized,
but at the same time it mixes consumer-passable and internal flags, while
tolerating this part by explicitly clearing some of them.
Tighten the interface instead.
While here renumber the flags and denote the gap between the 2 variants.
Try to piggy back th renumber on the just bumped __FreeBSD_version.
This means there is no expectation lookup will purge the terminal entry,
which simplifies lockless lookup.
Tested by: pho
Sponsored by: The FreeBSD Foundation
Almost all consumers use the NDF_ONLY_PNBUF macro, making them avoidably branch
a lot in the NDFREE routine. Also note most of them should not need to call
any cleanup anyway as they don't request HASBUF.
Provides full scalability as long as all visited filesystems support the
lookup and terminal vnodes are different.
Inner workings are explained in the comment above cache_fplookup.
Capabilities and fd-relative lookups are not supported and will result in
immediate fallback to regular code.
Symlinks, ".." in the path, mount points without support for lockless lookup
and mismatched counters will result in an attempt to get a reference to the
directory vnode and continue in regular lookup. If this fails, the entire
operation is aborted and regular lookup starts from scratch. However, care is
taken that data is not copied again from userspace.
Sample benchmark:
incremental -j 104 bzImage on tmpfs:
before: 142.96s user 1025.63s system 4924% cpu 23.731 total
after: 147.36s user 313.40s system 3216% cpu 14.326 total
Sample microbenchmark: access calls to separate files in /tmpfs, 104 workers, ops/s:
before: 2165816
after: 151216530
Reviewed by: kib
Tested by: pho (in a patchset)
Differential Revision: https://reviews.freebsd.org/D25578
They are spurious since introduction of struct pwd, which provides them
implicitly.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D23885
The new structure is copy-on-write. With the assumption that path lookups are
significantly more frequent than chdirs and chrooting this is a win.
This provides stable root and jail root vnodes without the need to reference
them on lookup, which in turn means less work on globally shared structures.
Note this also happens to fix a bug where jail vnode was never referenced,
meaning subsequent access on lookup could run into use-after-free.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D23884
Duplicating the work was putting an avoidable requirement that the filedesc
lock is held across the entire operation (otherwise by the time audit reads
vnode pointers another thread in the same process can chdir somewhere else,
making audit log things using different vnode than the one which will be
used for actual lookup).
Do the obvious thing and pass down vnodes which will be used.
Most notably, we want to make sure we don't clobber any capabilities-related
errors. This is a regression from r357412 (O_SEARCH) that was picked up by
the capsicum tests.
PR: 243839
Reviewed by: kib (committed form recommended by)
Tested by: lwhsu
Differential Revision: https://reviews.freebsd.org/D23479
O_SEARCH is defined by POSIX [0] to open a directory for searching, skipping
permissions checks on the directory itself after the initial open(). This is
close to the semantics we've historically applied for O_EXEC on a directory,
which is UB according to POSIX. Conveniently, O_SEARCH on a file is also
explicitly undefined behavior according to POSIX, so O_EXEC would be a fine
choice. The spec goes on to state that O_SEARCH and O_EXEC need not be
distinct values, but they're not defined to be the same value.
This was pointed out as an incompatibility with other systems that had made
its way into libarchive, which had assumed that O_EXEC was an alias for
O_SEARCH.
This defines compatibility O_SEARCH/FSEARCH (equivalent to O_EXEC and FEXEC
respectively) and expands our UB for O_EXEC on a directory. O_EXEC on a
directory is checked in vn_open_vnode already, so for completeness we add a
NOEXECCHECK when O_SEARCH has been specified on the top-level fd and do not
re-check that when descending in namei.
[0] https://pubs.opengroup.org/onlinepubs/9699919799/
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D23247
There are 2 back-to-back atomics on the vnode, but we can check upfront if one
is sufficient. Similarly we can handle relative lookups where current working
directory == root directory.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D23427
Filesystems which want to use it in limited capacity can employ the
VOP_UNLOCK_FLAGS macro.
Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D21427
The current vnode layout is not smp-friendly by having frequently read data
avoidably sharing cachelines with very frequently modified fields. In
particular v_iflag inspected for VI_DOOMED can be found in the same line with
v_usecount. Instead make it available in the same cacheline as the v_op, v_data
and v_type which all get read all the time.
v_type is avoidably 4 bytes while the necessary data will easily fit in 1.
Shrinking it frees up 3 bytes, 2 of which get used here to introduce a new
flag field with a new value: VIRF_DOOMED.
Reviewed by: kib, jeff
Differential Revision: https://reviews.freebsd.org/D22715
NDFREE() calculates unlock_dvp after ndp->ni_vp is unlocked and zeroed
out. This makes the comparision of ni_dvp with ni_vp always fail.
Move the calculation of unlock_dvp right after unlock_vp, so that the
code sees correct ni_vp value.
Reproduced by
chdir("/usr");
open("/..", O_BENEATH | O_RDONLY);
Reported by: syzkaller
Reviewed by: markj, mckusick
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D20304
When renameat(2) is used with:
- absolute path for to;
- tofd not set to AT_FDCWD;
- the target exists
kern_renameat() requires CAP_UNLINK capability on tofd, but
corresponding namei ni_filecap is not initialized at all because the
lookup is absolute. As result, the check was done against empty filecap
and syscall fails erronously.
Fix it by creating a return flags namei member and reporting if the
lookup was absolute, then do not touch to.ni_filecaps at all.
PR: 222258
Reviewed by: jilles, ngie
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
X-MFC-note: KBI breakage
Differential revision: https://reviews.freebsd.org/D19096
1) filecaps_init was unnecesarily a function call
2) an asignment at the end was preventing tail calling of cap_rights_init
Sponsored by: The FreeBSD Foundation
It is possible that we started with a relative path but during the
lookup, found an absolute symlink. In this case, BENEATH handling
code needs the latch, but it is too late to calculate it.
While there, somewhat improve the assertions. Clear the NI_LCF_LATCH
flag when the latch vnode is released, so that asserts know the state.
Assert that there is a latch if we entered beneath+abs path mode,
after the starting point is processed.
Reported by: wulf
With more input from: pho
Sponsored by: The FreeBSD Foundation
The path must have a tail which does not escape starting/topping
directory. The documentation will come shortly, see the man pages
commit message for the reason of separate commit.
Reviewed by: jilles (previous version)
Discussed with: emaste
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D17714
Flags prevent open(2) and *at(2) vfs syscalls name lookup from
escaping the starting directory. Supposedly the interface is similar
to the same proposed Linux flags.
Reviewed by: jilles (code, previous version of manpages), 0mp (manpages)
Discussed with: allanjude, emaste, jonathan
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D17547
