[Bug libc/11082] fclose(f); ftell(f); results in accesses on free'd memory

[Bug libc/11082] fclose(f); ftell(f); results in accesses on free'd memory

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=11082

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
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              Flags|                            |security-

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[Bug libc/11082] fclose(f); ftell(f); results in accesses on free'd memory

[pasky at suse dot cz]

------- Additional Comments From pasky at suse dot cz  2009-12-11 13:24 -------
Not really, file descriptor is something different from file stream. Something
can close the file descriptor while keeping the stream alive (e.g. by obtaining
it from stream using fileno() or by mass-closing all file descriptors), then
this error would trigger.

But if you close the stream itself, there's no stream _of_ the underlying file
descriptor. After you fclose(), the FILE* value is totally invalid and you must
not use it anymore.

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           What    |Removed                     |Added
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             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID


http://sourceware.org/bugzilla/show_bug.cgi?id=11082

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[Bug libc/11082] fclose(f); ftell(f); results in accesses on free'd memory

[jur dot pauw at gmail dot com]

------- Additional Comments From jur dot pauw at gmail dot com  2009-12-11 13:12 -------
(In reply to comment #1)
> ftell(3) needs a valid FILE pointer, not one already invalidated by fclose(3)
> call.  For details see fclose(3) description that says: "any further access 
to
> the stream results in undefined behaviour".

This implies that ftell its behaviour is not Posix compliant, see 
http://www.opengroup.org/onlinepubs/009695399/functions/ftell.html

ERRORS
The ftell() [CX]   and ftello()  functions shall fail if:

[EBADF] 
[CX]  The file descriptor underlying stream is not an open file descriptor.  


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           What    |Removed                     |Added
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             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |


http://sourceware.org/bugzilla/show_bug.cgi?id=11082

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[Bug libc/11082] fclose(f); ftell(f); results in accesses on free'd memory

[ldv at altlinux dot org]

------- Additional Comments From ldv at altlinux dot org  2009-12-11 11:10 -------
ftell(3) needs a valid FILE pointer, not one already invalidated by fclose(3)
call.  For details see fclose(3) description that says: "any further access to
the stream results in undefined behaviour".

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           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


http://sourceware.org/bugzilla/show_bug.cgi?id=11082

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