[Bug time/19179] New: gmtime_r internally calls getenv("TZ") which is not thread-safe

[Bug time/19179] New: gmtime_r internally calls getenv("TZ") which is not thread-safe

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19179

            Bug ID: 19179
           Summary: gmtime_r internally calls getenv("TZ") which is not
                    thread-safe
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: time
          Assignee: unassigned at sourceware dot org
          Reporter: nszabolcs at gmail dot com
  Target Milestone: ---

gmtime_r should be thread-safe, but it calls tzset_internal which calls
getenv("TZ") which is non-thread-safe.

a multi-threaded application may modify the TZ env var through the
environ pointer if there is no concurrent access to this env var in
other threads.

gmtime_r is not specified to access TZ, if it does, that can introduce
a data race in a conforming application and gmtime_r may misbehave if
it observes TZ in an inconsistent state.

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[Bug time/19179] gmtime_r internally calls getenv("TZ") which is not thread-safe

[ppluzhnikov at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19179

Paul Pluzhnikov <ppluzhnikov at google dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |ppluzhnikov at google dot com
         Resolution|---                         |DUPLICATE

--- Comment #1 from Paul Pluzhnikov <ppluzhnikov at google dot com> ---
Dup of 14023

*** This bug has been marked as a duplicate of bug 14023 ***

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[Bug time/19179] gmtime_r internally calls getenv("TZ") which is not thread-safe

[ppluzhnikov at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19179

--- Comment #2 from Paul Pluzhnikov <ppluzhnikov at google dot com> ---
getenv is thread-safe (so long as other threads aren't modifying the
environment), so if getenv() was the problem, this bug would be invalid.

But tzset_internal writes globals, and is definitely not thread-safe.

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[Bug time/19179] gmtime_r internally calls getenv("TZ") which is not thread-safe

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19179

--- Comment #3 from Szabolcs Nagy <nszabolcs at gmail dot com> ---
i used the wrong words there.

getenv is thread-safe, but an application is
allowed to modify an env var concurrently with
a thread-safe function except if the function
is specified to access the environment.

gmtime_r is not specified to access the env,
so it is not allowed to call getenv.

(i.e. unconditionally thread-safe functions are
not allowed to call conditionally thread-safe
ones.)

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