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Chuck Lever 84c1adb60f perf synthetic-events: Fix stale build ID in module MMAP2 records 
[ Upstream commit 35b16a7a2c ]

perf_event__synthesize_modules() allocates a single union perf_event and
reuses it across every kernel module callback.

After the first module is processed, perf_record_mmap2__read_build_id()
sets PERF_RECORD_MISC_MMAP_BUILD_ID in header.misc and writes that
module's build ID into the event.

On subsequent iterations the callback overwrites start, len, pid, and
filename for the next module but never clears the stale build ID fields
or the MMAP_BUILD_ID flag.

When perf_record_mmap2__read_build_id() runs for the second module it
sees the flag, reads the stale build ID into a dso_id, and
__dso__improve_id() permanently poisons the DSO with the wrong build ID.

Every module after the first therefore receives the first module's build
ID in its MMAP2 record.

On a system with the sunrpc and nfsd modules loaded, this causes perf
script and perf report to show [unknown] for all module symbols.

The latent bug has existed since commit d9f2ecbc5e ("perf dso:
Move build_id to dso_id") introduced the PERF_RECORD_MISC_MMAP_BUILD_ID
check in perf_record_mmap2__read_build_id().

Commit 53b00ff358 ("perf record: Make --buildid-mmap the default")
then exposed it to all users by making the MMAP2-with-build-ID path the
default.  Both commits were merged in the same series.

Clear the MMAP_BUILD_ID flag and zero the build_id union before each
call to perf_record_mmap2__read_build_id() so that every module starts
with a clean slate.

Fixes: d9f2ecbc5e ("perf dso: Move build_id to dso_id")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-19 16:08:20 +01:00
arch powerpc: 83xx: km83xx: Fix keymile vendor prefix 2026-03-19 16:08:12 +01:00
block block: use trylock to avoid lockdep circular dependency in sysfs 2026-03-12 07:09:59 -04:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation dt-bindings: display/msm: qcom,sm8750-mdss: Fix model typo 2026-03-19 16:08:13 +01:00
drivers drm/amdkfd: Unreserve bo if queue update failed 2026-03-19 16:08:20 +01:00
fs rxrpc, afs: Fix missing error pointer check after rxrpc_kernel_lookup_peer() 2026-03-19 16:08:14 +01:00
include page_pool: store detach_time as ktime_t to avoid false-negatives 2026-03-19 16:08:20 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: fix user_ref race between scrub and refill paths 2026-03-04 07:21:33 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel sched: idle: Make skipping governor callbacks more consistent 2026-03-19 16:08:19 +01:00
lib debugobject: Make it work with deferred page initialization - again 2026-03-12 07:09:08 -04:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm: thp: deny THP for files on anonymous inodes 2026-03-12 07:09:41 -04:00
net page_pool: store detach_time as ktime_t to avoid false-negatives 2026-03-19 16:08:20 +01:00
rust rust: kunit: fix warning when !CONFIG_PRINTK 2026-03-12 07:09:52 -04:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts kbuild: rpm-pkg: Disable automatic requires for manual debuginfo package 2026-03-04 07:21:32 -05:00
security apparmor: fix race between freeing data and fs accessing it 2026-03-13 17:23:30 +01:00
sound ASoC: detect empty DMI strings 2026-03-19 16:08:20 +01:00
tools perf synthetic-events: Fix stale build ID in module MMAP2 records 2026-03-19 16:08:20 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.18 2026-03-13 17:23:30 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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 reStructuredText 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.