4eb559dd15
Fuzz testing of the refcount btree demonstrated a weakness in validation
of refcount btree records during normal runtime. The idea of using the
upper bit of the rc_startblock field to separate the refcount records
into one group for shared space and another for CoW staging extents was
added at the last minute. The incore struct left this bit encoded in
the upper bit of the startblock field, which makes it all too easy for
arithmetic operations to overflow if we don't detect the cowflag
properly.
When I ran a norepair fuzz tester, I was able to crash the kernel on one
of these accidental overflows by fuzzing a key record in a node block,
which broke lookups. To fix the problem, make the domain (shared/cow) a
separate field in the incore record.
Unfortunately, a customer also hit this once in production. Due to bugs
in the kernel running on the VM host, writes to the disk image would
occasionally be lost. Given sufficient memory pressure on the VM guest,
a refcountbt xfs_buf could be reclaimed and later reloaded from the
stale copy on the virtual disk. The stale disk contents were a refcount
btree leaf block full of records for the wrong domain, and this caused
an infinite loop in the guest VM.
v2: actually include the refcount adjust loop invariant checking patch;
move the deferred refcount continuation checks earlier in the series;
break up the megapatch into smaller pieces; fix an uninitialized list
error.
v3: in the continuation check patch, verify the per-ag extent before
converting it to a fsblock
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
-----BEGIN PGP SIGNATURE-----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=PiZA
-----END PGP SIGNATURE-----
Merge tag 'refcount-cow-domain-6.1_2022-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.1-fixesA
xfs: improve runtime refcountbt corruption detection
Fuzz testing of the refcount btree demonstrated a weakness in validation
of refcount btree records during normal runtime. The idea of using the
upper bit of the rc_startblock field to separate the refcount records
into one group for shared space and another for CoW staging extents was
added at the last minute. The incore struct left this bit encoded in
the upper bit of the startblock field, which makes it all too easy for
arithmetic operations to overflow if we don't detect the cowflag
properly.
When I ran a norepair fuzz tester, I was able to crash the kernel on one
of these accidental overflows by fuzzing a key record in a node block,
which broke lookups. To fix the problem, make the domain (shared/cow) a
separate field in the incore record.
Unfortunately, a customer also hit this once in production. Due to bugs
in the kernel running on the VM host, writes to the disk image would
occasionally be lost. Given sufficient memory pressure on the VM guest,
a refcountbt xfs_buf could be reclaimed and later reloaded from the
stale copy on the virtual disk. The stale disk contents were a refcount
btree leaf block full of records for the wrong domain, and this caused
an infinite loop in the guest VM.
v2: actually include the refcount adjust loop invariant checking patch;
move the deferred refcount continuation checks earlier in the series;
break up the megapatch into smaller pieces; fix an uninitialized list
error.
v3: in the continuation check patch, verify the per-ag extent before
converting it to a fsblock
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
* tag 'refcount-cow-domain-6.1_2022-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
xfs: rename XFS_REFC_COW_START to _COWFLAG
xfs: fix uninitialized list head in struct xfs_refcount_recovery
xfs: fix agblocks check in the cow leftover recovery function
xfs: check record domain when accessing refcount records
xfs: remove XFS_FIND_RCEXT_SHARED and _COW
xfs: refactor domain and refcount checking
xfs: report refcount domain in tracepoints
xfs: track cow/shared record domains explicitly in xfs_refcount_irec
xfs: refactor refcount record usage in xchk_refcountbt_rec
xfs: move _irec structs to xfs_types.h
xfs: check deferred refcount op continuation parameters
xfs: create a predicate to verify per-AG extents
xfs: make sure aglen never goes negative in xfs_refcount_adjust_extents
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.