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sd-bus: make bus_error_message() a thread-safe macro

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strerror_r() is used instead of strerror(). The usual trick is employed: we
allocate a buffer that lives until the end of the surrounding block to provide
the scratch space. This change is particularly important forn sd-bus and the
pam modules, which may be called from threaded code.

I checked the codebase, and we only use bus_error_message() in log statements,
so the returned pointer is not used beyond its valid lifetime.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2022-10-07 15:56:25 +02:00
parent a390b03089
commit eaaf7465ee
2 changed files with 11 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/libsystemd/sd-bus/bus-error.c
View File

@@ -494,7 +494,7 @@ _public_ int sd_bus_error_set_errno(sd_bus_error *e, int error) {
*e = BUS_ERROR_FAILED;
}
/* Now, fill in the message from strerror() if we can */
/* Now, fill in the message from strerror_r() if we can */
bus_error_strerror(e, error);
return -error;
}
@@ -555,7 +555,7 @@ _public_ int sd_bus_error_set_errnofv(sd_bus_error *e, int error, const char *fo
}
fail:
/* If that didn't work, use strerror() for the message */
/* If that didn't work, use strerror_r() for the message */
bus_error_strerror(e, error);
return -error;
}
@@ -586,7 +586,7 @@ _public_ int sd_bus_error_set_errnof(sd_bus_error *e, int error, const char *for
return sd_bus_error_set_errno(e, error);
}
const char *bus_error_message(const sd_bus_error *e, int error) {
const char* _bus_error_message(const sd_bus_error *e, int error, char buf[static ERRNO_BUF_LEN]) {
/* Sometimes, the D-Bus server is a little bit too verbose with
* its error messages, so let's override them here */
if (sd_bus_error_has_name(e, SD_BUS_ERROR_ACCESS_DENIED))
@@ -595,7 +595,7 @@ const char *bus_error_message(const sd_bus_error *e, int error) {
if (e && e->message)
return e->message;
return strerror_safe(error);
return strerror_r(abs(error), buf, ERRNO_BUF_LEN);
}
static bool map_ok(const sd_bus_error_map *map) {

8
src/libsystemd/sd-bus/bus-error.h
View File

@@ -5,11 +5,17 @@
#include "sd-bus.h"
#include "errno-util.h"
#include "macro.h"
bool bus_error_is_dirty(sd_bus_error *e);
const char *bus_error_message(const sd_bus_error *e, int error);
const char* _bus_error_message(const sd_bus_error *e, int error, char buf[static ERRNO_BUF_LEN]);
/* Note: the lifetime of the compound literal is the immediately surrounding block,
* see C11 §6.5.2.5, and
* https://stackoverflow.com/questions/34880638/compound-literal-lifetime-and-if-blocks */
#define bus_error_message(e, error) _bus_error_message(e, error, (char[ERRNO_BUF_LEN]){})
#define BUS_ERROR_OOM SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_NO_MEMORY, "Out of memory")
#define BUS_ERROR_FAILED SD_BUS_ERROR_MAKE_CONST(SD_BUS_ERROR_FAILED, "Operation failed")