From 38d7a52bcdad1cef1dba218f86e3905c24d51d9a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Tue, 29 Apr 2025 14:47:59 +0200 Subject: [PATCH] coredump: restore compatibility with older patterns This was broken in f45b8015513d38ee5f7cc361db9c5b88c9aae704. Unfortunately the review does not talk about backward compatibility at all. There are two places where it matters: - During upgrades, the replacement of kernel.core_pattern is asynchronous. For example, during rpm upgrades, it would be updated a post-transaction file trigger. In other scenarios, the update might only happen after reboot. We have a potentially long window where the old pattern is in place. We need to capture coredumps during upgrades too. - With --backtrace. The interface of --backtrace, in hindsight, is not great. But there are users of --backtrace which were written to use a specific set of arguments, and we can't just break compatiblity. One example is systemd-coredump-python, but there are also reports of users using --backtrace to generate coredump logs. Thus, we require the original set of args, and will use the additional args if found. A test is added to verify that --backtrace works with and without the optional args. (cherry picked from commit ded0aac389e647d35bce7ec4a48e718d77c0435b) Related: RHEL-104138 --- src/coredump/coredump.c | 23 +++++++++++++++-------- test/units/testsuite-74.coredump.sh | 18 +++++++++++------- 2 files changed, 26 insertions(+), 15 deletions(-) diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c index b24f4c8cc3..458857ffb2 100644 --- a/src/coredump/coredump.c +++ b/src/coredump/coredump.c @@ -94,8 +94,12 @@ enum { META_ARGV_SIGNAL, /* %s: number of signal causing dump */ META_ARGV_TIMESTAMP, /* %t: time of dump, expressed as seconds since the Epoch (we expand this to µs granularity) */ META_ARGV_RLIMIT, /* %c: core file size soft resource limit */ - META_ARGV_HOSTNAME, /* %h: hostname */ + _META_ARGV_REQUIRED, + /* The fields below were added to kernel/core_pattern at later points, so they might be missing. */ + META_ARGV_HOSTNAME = _META_ARGV_REQUIRED, /* %h: hostname */ _META_ARGV_MAX, + /* If new fields are added, they should be added here, to maintain compatibility + * with callers which don't know about the new fields. */ /* The following indexes are cached for a couple of special fields we use (and * thereby need to be retrieved quickly) for naming coredump files, and attaching @@ -106,7 +110,7 @@ enum { _META_MANDATORY_MAX, /* The rest are similar to the previous ones except that we won't fail if one of - * them is missing. */ + * them is missing in a message sent over the socket. */ META_EXE = _META_MANDATORY_MAX, META_UNIT, @@ -1068,7 +1072,7 @@ static int save_context(Context *context, const struct iovec_wrapper *iovw) { } /* The basic fields from argv[] should always be there, refuse early if not */ - for (int i = 0; i < _META_ARGV_MAX; i++) + for (int i = 0; i < _META_ARGV_REQUIRED; i++) if (!context->meta[i]) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "A required (%s) has not been sent, aborting.", meta_field_names[i]); @@ -1286,14 +1290,17 @@ static int gather_pid_metadata_from_argv( char *t; /* We gather all metadata that were passed via argv[] into an array of iovecs that - * we'll forward to the socket unit */ + * we'll forward to the socket unit. + * + * We require at least _META_ARGV_REQUIRED args, but will accept more. + * We know how to parse _META_ARGV_MAX args. The rest will be ignored. */ - if (argc < _META_ARGV_MAX) + if (argc < _META_ARGV_REQUIRED) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), - "Not enough arguments passed by the kernel (%i, expected %i).", - argc, _META_ARGV_MAX); + "Not enough arguments passed by the kernel (%i, expected between %i and %i).", + argc, _META_ARGV_REQUIRED, _META_ARGV_MAX); - for (int i = 0; i < _META_ARGV_MAX; i++) { + for (int i = 0; i < MIN(argc, _META_ARGV_MAX); i++) { t = argv[i]; diff --git a/test/units/testsuite-74.coredump.sh b/test/units/testsuite-74.coredump.sh index 1093cad8a9..0163131096 100755 --- a/test/units/testsuite-74.coredump.sh +++ b/test/units/testsuite-74.coredump.sh @@ -218,14 +218,18 @@ rm -f /tmp/core.{output,redirected} (! "${UNPRIV_CMD[@]}" coredumpctl dump "$CORE_TEST_BIN" >/dev/null) # --backtrace mode -# Pass one of the existing journal coredump records to systemd-coredump and -# use our PID as the source to make matching the coredump later easier -# systemd-coredump args: PID UID GID SIGNUM TIMESTAMP CORE_SOFT_RLIMIT HOSTNAME +# Pass one of the existing journal coredump records to systemd-coredump. +# Use our PID as the source to be able to create a PIDFD and to make matching easier. +# systemd-coredump args: PID UID GID SIGNUM TIMESTAMP CORE_SOFT_RLIMIT [HOSTNAME] journalctl -b -n 1 --output=export --output-fields=MESSAGE,COREDUMP COREDUMP_EXE="/usr/bin/test-dump" | - /usr/lib/systemd/systemd-coredump --backtrace $$ 0 0 6 1679509994 12345 mymachine -# Wait a bit for the coredump to get processed -timeout 30 bash -c "while [[ \$(coredumpctl list -q --no-legend $$ | wc -l) -eq 0 ]]; do sleep 1; done" -coredumpctl info "$$" + /usr/lib/systemd/systemd-coredump --backtrace $$ 0 0 6 1679509900 12345 +journalctl -b -n 1 --output=export --output-fields=MESSAGE,COREDUMP COREDUMP_EXE="/usr/bin/test-dump" | + /usr/lib/systemd/systemd-coredump --backtrace $$ 0 0 6 1679509901 12345 mymachine +# Wait a bit for the coredumps to get processed +timeout 30 bash -c "while [[ \$(coredumpctl list -q --no-legend $$ | wc -l) -lt 2 ]]; do sleep 1; done" +coredumpctl info $$ +coredumpctl info COREDUMP_TIMESTAMP=1679509900000000 +coredumpctl info COREDUMP_TIMESTAMP=1679509901000000 coredumpctl info COREDUMP_HOSTNAME="mymachine" # This used to cause a stack overflow