[Bug libc/4350] New: Reentrancy problem between strftime() and setenv()

[Bug libc/4350] New: Reentrancy problem between strftime() and setenv()

[pasky at suse dot cz]

Threaded programs may crash randomly if strftime() and setenv() aren't excluded
from being called in parallel, since getenv() is called from the inside of
strftime(). While getenv()-setenv() thread safety problems are documented, it is
not documented that time functions have these problems as well. The proposed
patch introduces getenv_r() as a reentrant version of getenv() and uses it from
inside of the time functions; maybe you'll choose a different approach (or a
different name for the function or so), but something should be done about this.
Also, maybe other parts of glibc making use of getenv() might need the same fix.

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           Summary: Reentrancy problem between strftime() and setenv()
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: pasky at suse dot cz
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=4350

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[Bug libc/4350] Reentrancy problem between strftime() and setenv()

[pasky at suse dot cz]

------- Additional Comments From pasky at suse dot cz  2007-04-12 14:43 -------
Created an attachment (id=1676)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=1676&action=view)
Proposed patch


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[Bug libc/4350] Reentrancy problem between strftime() and setenv()

[pasky at suse dot cz]

------- Additional Comments From pasky at suse dot cz  2007-04-12 14:45 -------
(Forgot to mention that the patch was written only partially by me, a large part
came from a customer of Novell.)

-- 


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[Bug libc/4350] Reentrancy problem between strftime() and setenv()

[jakub at redhat dot com]

------- Additional Comments From jakub at redhat dot com  2007-04-13 18:50 -------
strftime is documented in POSIX that it acts as if it calls tzset().
And tzset is documented to inspect the TZ env variable.
setenv is documented to be non-thread safe, what glibc does there is beyond
what the standard requires.  And this is IMHO the same thing.

-- 


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[Bug libc/4350] Reentrancy problem between strftime() and setenv()

[pasky at suse dot cz]

------- Additional Comments From pasky at suse dot cz  2007-04-26 18:11 -------
Strictly speaking, it doesn't say that it inspects $TZ in a non-reentrant way
(using getenv()), does it? But I agree that this is quite a nitpicking. But
still, what are the considerations against integrating such a patch? Just the
possible small performance penalty?

-- 


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