diff options
| author | Jake Edge <jake@lwn.net> | 2009-05-04 12:51:14 -0600 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-05-04 15:14:23 -0700 |
| commit | f83ce3e6b02d5e48b3a43b001390e2b58820389d (patch) | |
| tree | 71c57abf4f9d259f5bfa22deaf724db85738f862 | |
| parent | 7fdf523067666b0eaff330f362401ee50ce187c4 (diff) | |
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 <stable@kernel.org>
Signed-off-by: Jake Edge <jake@lwn.net>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/proc/array.c | 13 | ||||
| -rw-r--r-- | fs/proc/base.c | 5 |
2 files changed, 13 insertions, 5 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c index 7e4877d9dcb..725a650bbbb 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -80,6 +80,7 @@ #include <linux/delayacct.h> #include <linux/seq_file.h> #include <linux/pid_namespace.h> +#include <linux/ptrace.h> #include <linux/tracehook.h> #include <asm/pgtable.h> @@ -352,6 +353,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, char state; pid_t ppid = 0, pgid = -1, sid = -1; int num_threads = 0; + int permitted; struct mm_struct *mm; unsigned long long start_time; unsigned long cmin_flt = 0, cmaj_flt = 0; @@ -364,11 +366,14 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, state = *get_task_state(task); vsize = eip = esp = 0; + permitted = ptrace_may_access(task, PTRACE_MODE_READ); mm = get_task_mm(task); if (mm) { vsize = task_vsize(mm); - eip = KSTK_EIP(task); - esp = KSTK_ESP(task); + if (permitted) { + eip = KSTK_EIP(task); + esp = KSTK_ESP(task); + } } get_task_comm(tcomm, task); @@ -424,7 +429,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, unlock_task_sighand(task, &flags); } - if (!whole || num_threads < 2) + if (permitted && (!whole || num_threads < 2)) wchan = get_wchan(task); if (!whole) { min_flt = task->min_flt; @@ -476,7 +481,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, rsslim, mm ? mm->start_code : 0, mm ? mm->end_code : 0, - mm ? mm->start_stack : 0, + (permitted && mm) ? mm->start_stack : 0, esp, eip, /* The signal information here is obsolete. diff --git a/fs/proc/base.c b/fs/proc/base.c index aa763ab0077..fb45615943c 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); } |