[PATCH] coredump filter: fix stack overflow with =all

We translate 'all' to UNIT64_MAX, which has a lot more 'f's. Use the
helper macro, since a decimal uint64_t will always be >> than a hex
representation.

root@image:~# systemd-run -t --property CoredumpFilter=all ls /tmp
Running as unit: run-u13.service
Press ^] three times within 1s to disconnect TTY.
*** stack smashing detected ***: terminated
[137256.320511] systemd[1]: run-u13.service: Main process exited, code=dumped, status=6/ABRT
[137256.320850] systemd[1]: run-u13.service: Failed with result 'core-dump'.

Origin: upstream, https://github.com/systemd/systemd/commit/37232d55a7bcace37280e28b207c85f5ca9b3f6b
Forwarded: not-needed
Last-Update: 2025-07-27

Gbp-Pq: Name fix-stack-overflow-in-coredump-filter-0.patch

diff --git a/src/basic/macro.h b/src/basic/macro.h
index e57014ceb9c4e5714bb063c4e76b7c59333aaf00..1413ca716243fb56beceee65d3462b0c043360fa 100644 (file)
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -472,6 +472,10 @@ static inline int __coverity_check_and_return__(int condition) {
 
 #define sizeof_field(struct_type, member) sizeof(((struct_type *) 0)->member)
 
+/* Maximum buffer size needed for formatting an unsigned integer type as hex, including space for '0x'
+ * prefix and trailing NUL suffix. */
+#define HEXADECIMAL_STR_MAX(type) (2 + sizeof(type) * 2 + 1)
+
 /* Returns the number of chars needed to format variables of the
  * specified type as a decimal string. Adds in extra space for a
  * negative '-' prefix (hence works correctly on signed

diff --git a/src/shared/coredump-util.c b/src/shared/coredump-util.c
index a0b648bf791887c116c957bd0efe0e9964e6a380..aaf3e16eff08d917e39e9c16667b80a73cad2a7a 100644 (file)
--- a/src/shared/coredump-util.c
+++ b/src/shared/coredump-util.c
@@ -3,6 +3,7 @@
 #include "coredump-util.h"
 #include "extract-word.h"
 #include "fileio.h"
+#include "stdio-util.h"
 #include "string-table.h"
 
 static const char *const coredump_filter_table[_COREDUMP_FILTER_MAX] = {
@@ -65,9 +66,9 @@ int coredump_filter_mask_from_string(const char *s, uint64_t *ret) {
 }
 
 int set_coredump_filter(uint64_t value) {
-        char t[STRLEN("0xFFFFFFFF")];
+        char t[HEXADECIMAL_STR_MAX(uint64_t)];
 
-        sprintf(t, "0x%"PRIx64, value);
+        xsprintf(t, "0x%"PRIx64, value);
 
         return write_string_file("/proc/self/coredump_filter", t,
                                  WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_DISABLE_BUFFER);