RE: Signal Handler

["Mathew, Tisson K" <tisson dot k dot mathew at intel dot com>]

Thanks Roland,

Does msgsnd use any of the heap-management routines like 'malloc'?
Referencing to an article at
http://razor.bindview.com/publish/papers/signals.txt about signal-handling
related vulnerabilities. A quote from this article
"
A) re-entering libc functions:

  Every function that is not listed as reentry-safe is a potential source 
  of vulnerabilities. Indeed, numerous library functions are operating 
  on global variables, and/or modify global state in non-atomic way.
  Once again, heap-management routines are probably the best example.
  By delivering a signal when malloc(), free() or any other libcall of
  this kind is being called, all subsequent calls to the heap management
  routines made from signal handler would have unpredictable effect,
  as heap state is completely unpredictable for the programmer.
"

Is this true for glibc as well ?

-Tisson 


-----Original Message-----
From: Roland McGrath [mailto:roland@redhat.com] 
Sent: Monday, November 25, 2002 1:39 PM
To: Mathew, Tisson K
Cc: 'libc-alpha@sources.redhat.com'
Subject: Re: Signal Handler


> Is it safe to invoke memset and msgsnd inside a signal handler? (I'm 
> thinking of using them inside SIGALRM handler)

You are not guaranteed this, but in practice it will be ok for those two.