ADD_SAFE/SUB_SAFE/MUL_SAFE do addition/subtraction/multiplication
respectively with an overflow check. If an overflow occurs these return
false, otherwise true. Example: (c = a + b) would become ADD_SAFE(&c, a,
b)
INC_SAFE/DEC_SAFE/MUL_ASSIGN_SAFE are like above but they also reassign
the first argument. Example: (a += b) would become INC_SAFE(&a, b)
We use it for more than just pipe() arrays. For example also for
socketpair(). Hence let's give it a generic name.
Also add EBADF_TRIPLET to mirror this for things like
stdin/stdout/stderr arrays, which we use a bunch of times.
We usually check return value of syscalls or glibc functions by it is
negative or not, something like that `if (stat(path, &st) < 0)`.
Let's also use the same style for lseek() and friends even the type of
their return value is off_t.
Note, fseeko() returns int, instead of off_t.
json_append() is a useful wrapper around json_variant_merge(). However,
I think the naming sould be cleaned up a bit of both functions.
I thinker "merge" is the better word than "append", since it does
decidedly more than just append: it replaces existing fields of the same
name, hence "merge" sounds more appropriate. This is as opposed to the
similar operations for arrays, where no such override logic is applied
and we really just append, hence those functions are called "append"
already.
To make clearer that "merge" is about objects, and "append" about
arrays, also include "object" in the name.
Also, include "json_variant" in the name, like we do for almost all
other functions in the JSON API that take a JSON object as primary
input, and hence are kinda object methods.
Finally, let's follow the logic that helpers that combine json_build()
with some other operation get suffixed with "b" like we already have in
some cases.
Hence:
json_variant_merge() → json_variant_merge_object()
json_append() → json_variant_merge_objectb()
This mirrors nicely the existing:
json_variant_append_array()
json_vairant_append_arrayb()
This also drops the variant of json_append() that takes a va_arg
parameter (i.e. json_appendv()). We have no user of that so far, and
given the nature as a helper function only I don#t see that happening,
and if it happens after all it's trivial to bring back.
Indeed when iterating over all the PT_LOAD segment of the core dump
while trying to look for the elf headers of a given module, we iterate
over them all and try to use the first one for which we can parse a
package metadata, but the start address is never taken into account,
so absolutely nothing guarantees we actually parse the right ELF header
of the right module we are currently iterating on.
This was tested like this:
- Create a core dump using sleep on a fedora 37 container, with an
explicit LD_PRELOAD of a library having a valid package metadata:
podman run -t -i --rm -v $(pwd):$(pwd) -w $(pwd) fedora:37 bash -x -c \
'LD_PRELOAD=libreadline.so.8 sleep 1000 & SLEEP_PID="$!" && sleep 1 && kill -11 "${SLEEP_PID}" && mv "core.${SLEEP_PID}" the-core'
- Then from a fedora 38 container with systemd installed, the resulting
core dump has been passed to systemd-coredump with and without this
patch. Without this patch, we get:
Module /usr/bin/sleep from rpm bash-5.2.15-3.fc38.x86_64
Module /usr/lib64/libtinfo.so.6.3 from rpm coreutils-9.1-8.fc37.x86_64
Module /usr/lib64/libc.so.6 from rpm coreutils-9.1-8.fc37.x86_64
Module /usr/lib64/libreadline.so.8.2 from rpm coreutils-9.1-8.fc37.x86_64
Module /usr/lib64/ld-linux-x86-64.so.2 from rpm coreutils-9.1-8.fc37.x86_64
While with this patch we get:
Module /usr/bin/sleep from rpm bash-5.2.15-3.fc38.x86_64
Module /usr/lib64/libtinfo.so.6.3 from rpm ncurses-6.3-5.20220501.fc37.x86_64
Module /usr/lib64/libreadline.so.8.2 from rpm readline-8.2-2.fc37.x86_64
So the parsed package metadata reported by systemd-coredump when the module
files are not found on the host (ie the case of crash inside a container) are
now correct. The inconsistency of the first module in the above example
(sleep is indeed not provided by the bash package) can be ignored as it
is a consequence of how this was tested.
In addition to this, this also fixes the performance issue of
systemd-coredump in case of the crashing process uses a large number of
shared libraries and having no package metadata, as reported in
https://sourceware.org/pipermail/elfutils-devel/2023q2/006225.html.
When closing the FILE handle attached to a memstream, it may attempt to
do a realloc() that may fail during OOM situations, in which case we are
left with the buffer pointer pointing to NULL and buffer size > 0. For
example:
```
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
void *realloc(void *ptr, size_t size) {
return NULL;
}
int main(int argc, char *argv[])
{
FILE *f;
char *buf;
size_t sz = 0;
f = open_memstream(&buf, &sz);
if (!f)
return -ENOMEM;
fputs("Hello", f);
fflush(f);
printf("buf: 0x%lx, sz: %lu, errno: %d\n",
(unsigned long) buf, sz, errno);
fclose(f);
printf("buf: 0x%lx, sz: %lu, errno: %d\n",
(unsigned long) buf, sz, errno);
return 0;
}
```
```
$ gcc -o main main.c
$ ./main
buf: 0x74d4a0, sz: 5, errno: 0
buf: 0x0, sz: 5, errno: 0
```
This might do unexpected things if the underlying code expects a valid
pointer to the memstream buffer after closing the handle.
Found by Nallocfuzz.
In both cases, the json string is short, so we can print it, which is useful
for diagnosing invalid data in packages. But we need escape non-printable
characters.
https://bugzilla.redhat.com/show_bug.cgi?id=2152685
I went over the rest of the codebase, and it seems that other calls to
json_parse() don't have this problem.
We would deadlock when passing the data back from the forked-off process that
was doing backtrace generation back to the coredump parent. This is because we
fork the child and wait for it to exit. The child tries to write too much data
to the output pipe, and and after the first 64k blocks on the parent because
the pipe is full. The bug surfaced in Fedora because of a combination of four
factors:
- 87707784c7 was backported to v251.5, which
allowed coredump processing to be successful.
- 1a0281a3eb was NOT backported, so the output
was very verbose.
- Fedora has the ELF package metadata available, so a lot of output can be
generated. Most other distros just don't have the information.
- gnome-calendar crashes and has a bazillion modules and 69596 bytes of output
are generated for it.
Fixes https://bugzilla.redhat.com/show_bug.cgi?id=2135778.
The code is changed to try to write data opportunistically. If we get partial
information, that is still logged. In is generally better to log partial
backtrace information than nothing at all.
Add dlopen_dw(), dlopen_elf() and dlopen_pcre2() to the dlopen test.
To enable adding dlopen_pcre2(), we move pcre2-dlopen.h/c from
src/journal to src/shared.
In order to avoid inflating the dependency list for the core
library, use dlopen when inspecting elfs, since it's only
used in two non-core executables.
Adrian Vovk
Frantisek Sumsal
Lennart Poettering
Yu Watanabe
Mike Yuan
Romain Geissler
Zbigniew Jędrzejewski-Szmek
David Tardon
Daan De Meyer
Luca Boccassi