From f83ce3e6b02d5e48b3a43b001390e2b58820389d Mon Sep 17 00:00:00 2001 From: Jake Edge Date: Mon, 4 May 2009 12:51:14 -0600 Subject: proc: avoid information leaks to non-privileged processes By using the same test as is used for /proc/pid/maps and /proc/pid/smaps, only allow processes that can ptrace() a given process to see information that might be used to bypass address space layout randomization (ASLR). These include eip, esp, wchan, and start_stack in /proc/pid/stat as well as the non-symbolic output from /proc/pid/wchan. ASLR can be bypassed by sampling eip as shown by the proof-of-concept code at http://code.google.com/p/fuzzyaslr/ As part of a presentation (http://www.cr0.org/paper/to-jt-linux-alsr-leak.pdf) esp and wchan were also noted as possibly usable information leaks as well. The start_stack address also leaks potentially useful information. Cc: Stable Team Signed-off-by: Jake Edge Acked-by: Arjan van de Ven Acked-by: "Eric W. Biederman" Signed-off-by: Linus Torvalds --- fs/proc/base.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'fs/proc/base.c') diff --git a/fs/proc/base.c b/fs/proc/base.c index aa763ab00777..fb45615943c2 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -322,7 +322,10 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer) wchan = get_wchan(task); if (lookup_symbol_name(wchan, symname) < 0) - return sprintf(buffer, "%lu", wchan); + if (!ptrace_may_access(task, PTRACE_MODE_READ)) + return 0; + else + return sprintf(buffer, "%lu", wchan); else return sprintf(buffer, "%s", symname); } -- cgit v1.2.3