proc: protect mm start_code/end_code in /proc/pid/stat
While mm->start_stack was protected from cross-uid viewing (commit f83ce3e6 ("proc: avoid information leaks to non-privileged processes")), the start_code and end_code values were not. This would allow the text location of a PIE binary to leak, defeating ASLR. Note that the value "1" is used instead of "0" for a protected value since "ps", "killall", and likely other readers of /proc/pid/stat, take start_code of "0" to mean a kernel thread and will misbehave. Thanks to Brad Spengler for pointing this out. Addresses CVE-2011-0726 Signed-off-by: Kees Cook <kees.cook@canonical.com> Cc: <stable@kernel.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Eugene Teo <eugeneteo@kernel.sg> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Brad Spengler <spender@grsecurity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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