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Commit202dbdb

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Make pgwin32_putenv() follow DLL loading and unloading.
Until now, the first putenv() call of a given postgres.exe process wouldcache the set of loaded CRTs. If a CRT unloaded after that call, thenext putenv() would crash. That risk was largely theoretical, becausethe first putenv() precedes all PostgreSQL-initiated module loading.However, this might explain bad interactions with antivirus and othersoftware that injects threads asynchronously. If an additional CRTloaded after the first putenv(), pgwin32_putenv() would not discover it.That CRT would have all environment changes predating its load, but itwould not receive later PostgreSQL-initiated changes. An additional CRTloading concurrently with the first putenv() might miss that change inaddition to missing later changes. Fix all those problems. Thisremoves the cache mechanism from pgwin32_putenv(); the cost, less than100 μs per backend startup, is negligible.No resulting misbehavior was known to be user-visible given the coredistribution alone, but one can readily construct an affected extensionmodule. No back-patch given the lack of complaints and the potentialfor behavior changes in non-PostgreSQL code running in the backend.Christian Ullrich, reviewed by Michael Paquier.
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1 file changed

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‎src/port/win32env.c

Lines changed: 48 additions & 112 deletions
Original file line numberDiff line numberDiff line change
@@ -21,126 +21,37 @@ pgwin32_putenv(const char *envval)
2121
{
2222
char*envcpy;
2323
char*cp;
24-
25-
/*
26-
* Each CRT has its own _putenv() symbol and copy of the environment.
27-
* Update the environment in each CRT module currently loaded, so every
28-
* third-party library sees this change regardless of the CRT it links
29-
* against.
30-
*/
3124
#ifdef_MSC_VER
3225
typedefint (_cdecl*PUTENVPROC) (constchar*);
33-
staticstruct
34-
{
35-
char*modulename;
36-
HMODULEhmodule;
37-
PUTENVPROCputenvFunc;
38-
}rtmodules[]=
39-
{
40-
{
41-
"msvcrt",NULL,NULL
42-
},/* Visual Studio 6.0 / MinGW */
43-
{
44-
"msvcrtd",NULL,NULL
45-
},
46-
{
47-
"msvcr70",NULL,NULL
48-
},/* Visual Studio 2002 */
49-
{
50-
"msvcr70d",NULL,NULL
51-
},
52-
{
53-
"msvcr71",NULL,NULL
54-
},/* Visual Studio 2003 */
55-
{
56-
"msvcr71d",NULL,NULL
57-
},
58-
{
59-
"msvcr80",NULL,NULL
60-
},/* Visual Studio 2005 */
61-
{
62-
"msvcr80d",NULL,NULL
63-
},
64-
{
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"msvcr90",NULL,NULL
66-
},/* Visual Studio 2008 */
67-
{
68-
"msvcr90d",NULL,NULL
69-
},
70-
{
71-
"msvcr100",NULL,NULL
72-
},/* Visual Studio 2010 */
73-
{
74-
"msvcr100d",NULL,NULL
75-
},
76-
{
77-
"msvcr110",NULL,NULL
78-
},/* Visual Studio 2012 */
79-
{
80-
"msvcr110d",NULL,NULL
81-
},
82-
{
83-
"msvcr120",NULL,NULL
84-
},/* Visual Studio 2013 */
85-
{
86-
"msvcr120d",NULL,NULL
87-
},
88-
{
89-
"ucrtbase",NULL,NULL
90-
},/* Visual Studio 2015 and later */
91-
{
92-
"ucrtbased",NULL,NULL
93-
},
94-
{
95-
NULL,NULL,NULL
96-
}
26+
staticconstchar*constmodulenames[]= {
27+
"msvcrt",/* Visual Studio 6.0 / MinGW */
28+
"msvcrtd",
29+
"msvcr70",/* Visual Studio 2002 */
30+
"msvcr70d",
31+
"msvcr71",/* Visual Studio 2003 */
32+
"msvcr71d",
33+
"msvcr80",/* Visual Studio 2005 */
34+
"msvcr80d",
35+
"msvcr90",/* Visual Studio 2008 */
36+
"msvcr90d",
37+
"msvcr100",/* Visual Studio 2010 */
38+
"msvcr100d",
39+
"msvcr110",/* Visual Studio 2012 */
40+
"msvcr110d",
41+
"msvcr120",/* Visual Studio 2013 */
42+
"msvcr120d",
43+
"ucrtbase",/* Visual Studio 2015 and later */
44+
"ucrtbased",
45+
NULL
9746
};
9847
inti;
99-
100-
for (i=0;rtmodules[i].modulename;i++)
101-
{
102-
if (rtmodules[i].putenvFunc==NULL)
103-
{
104-
if (rtmodules[i].hmodule==NULL)
105-
{
106-
/* Not attempted before, so try to find this DLL */
107-
rtmodules[i].hmodule=GetModuleHandle(rtmodules[i].modulename);
108-
if (rtmodules[i].hmodule==NULL)
109-
{
110-
/*
111-
* Set to INVALID_HANDLE_VALUE so we know we have tried
112-
* this one before, and won't try again.
113-
*/
114-
rtmodules[i].hmodule=INVALID_HANDLE_VALUE;
115-
continue;
116-
}
117-
else
118-
{
119-
rtmodules[i].putenvFunc= (PUTENVPROC)GetProcAddress(rtmodules[i].hmodule,"_putenv");
120-
if (rtmodules[i].putenvFunc==NULL)
121-
{
122-
rtmodules[i].hmodule=INVALID_HANDLE_VALUE;
123-
continue;
124-
}
125-
}
126-
}
127-
else
128-
{
129-
/*
130-
* Module loaded, but we did not find the function last time.
131-
* We're not going to find it this time either...
132-
*/
133-
continue;
134-
}
135-
}
136-
/* At this point, putenvFunc is set or we have exited the loop */
137-
rtmodules[i].putenvFunc(envval);
138-
}
13948
#endif/* _MSC_VER */
14049

14150
/*
14251
* Update process environment, making this change visible to child
143-
* processes and to CRTs initializing in the future.
52+
* processes and to CRTs initializing in the future. Do this before the
53+
* _putenv() loop, for the benefit of any CRT that initializes during this
54+
* pgwin32_putenv() execution, after the loop checks that CRT.
14455
*
14556
* Need a copy of the string so we can modify it.
14657
*/
@@ -170,6 +81,31 @@ pgwin32_putenv(const char *envval)
17081
}
17182
free(envcpy);
17283

84+
/*
85+
* Each CRT has its own _putenv() symbol and copy of the environment.
86+
* Update the environment in each CRT module currently loaded, so every
87+
* third-party library sees this change regardless of the CRT it links
88+
* against. Addresses within these modules may become invalid the moment
89+
* we call FreeLibrary(), so don't cache them.
90+
*/
91+
#ifdef_MSC_VER
92+
for (i=0;modulenames[i];i++)
93+
{
94+
HMODULEhmodule=NULL;
95+
BOOLres=GetModuleHandleEx(0,modulenames[i],&hmodule);
96+
97+
if (res!=0&&hmodule!=NULL)
98+
{
99+
PUTENVPROCputenvFunc;
100+
101+
putenvFunc= (PUTENVPROC)GetProcAddress(hmodule,"_putenv");
102+
if (putenvFunc)
103+
putenvFunc(envval);
104+
FreeLibrary(hmodule);
105+
}
106+
}
107+
#endif/* _MSC_VER */
108+
173109
/* Finally, update our "own" cache */
174110
return_putenv(envval);
175111
}

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