[Bug libc/10560] New: [PATCH] Avoid malloc deadlocks in assert() and friends

[Bug libc/10560] New: [PATCH] Avoid malloc deadlocks in assert() and friends

[ajax at redhat dot com]

In chasing a malloc bookkeeping corruption bug in X, I hit the following deadlock:

#1  0x00a66873 in __lll_lock_wait_private () from /lib/libc.so.6
#2  0x009ef8b4 in _L_lock_9686 () from /lib/libc.so.6
#3  0x009ed914 in malloc () from /lib/libc.so.6
#4  0x009e1718 in vasprintf () from /lib/libc.so.6
#5  0x009c3eeb in asprintf () from /lib/libc.so.6
#6  0x0099dc3d in __assert_fail () from /lib/libc.so.6
#7  0x009ec47d in _int_malloc () from /lib/libc.so.6
#8  0x009ed91e in malloc () from /lib/libc.so.6
#9  0x0095ba15 in pcfReadFont () from /usr/lib/libXfont.so.1
#10 0x0095667b in ?? () from /usr/lib/libXfont.so.1
#11 0x00949d03 in ?? () from /usr/lib/libXfont.so.1
#12 0x0095a11f in BitmapOpenScalable () from /usr/lib/libXfont.so.1
[...]

Not awesome.  There's a number of ways around this, the most straightforward of
which seems to be gcc variable-length arrays and sprintf'ing the error string
into that.  Attached patch does this.

Other options would include walking the args to __assert_fail() directly.  I
don't really have an opinion, and am willing to implement whatever is preferred.

-- 
           Summary: [PATCH] Avoid malloc deadlocks in assert() and friends
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: ajax at redhat dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10560

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[Bug libc/10560] [PATCH] Avoid malloc deadlocks in assert() and friends

[ajax at redhat dot com]

------- Additional Comments From ajax at redhat dot com  2009-08-25 19:03 -------
Created an attachment (id=4150)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=4150&action=view)
glibc-mallocless-assert.patch


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=10560

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[Bug libc/10560] [PATCH] Avoid malloc deadlocks in assert() and friends

[roland at gnu dot org]

------- Additional Comments From roland at gnu dot org  2009-08-25 19:19 -------
It's not at all clear to me why it doesn't use __fxprintf directly, or indeed
just use __dprintf.

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http://sourceware.org/bugzilla/show_bug.cgi?id=10560

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[Bug libc/10560] [PATCH] Avoid malloc deadlocks in assert() and friends

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-08-31 11:46 -------
The reason malloc is used is so that in case you see a core file but no console
output you know what was going on.  Using the stack memory is not sufficient in
this case.  The __abort_msg variable was deliberately introduced and is visible
to the debugger and other tools.

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http://sourceware.org/bugzilla/show_bug.cgi?id=10560

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[Bug libc/10560] [PATCH] Avoid malloc deadlocks in assert() and friends

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2009-08-31 11:57 -------
Fixed upstream.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=10560

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