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authorLinus Torvalds <torvalds@linux-foundation.org>2015-11-03 15:04:04 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-03 15:04:04 -0800
commit7eeef2abe87dc0d8c276f97ccfdb1f42d9d1e4d8 (patch)
tree69141bc10fab1bb9b8aaa94f87c617b9c813155c
parent6aa2fdb87cf01d7746955c600cbac352dc04d451 (diff)
parentb2f73922d119686323f14fbbe46587f863852328 (diff)
Merge branch 'core-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull wchan kernel address hiding from Ingo Molnar: "This fixes a wchan related information leak in /proc/PID/stat. There's a bit of an ABI twist to it: instead of setting the wchan field to 0 (which is our usual technique) we set it conditionally to a 0/1 flag to keep ABI compatibility with older procps versions that only fetches /proc/PID/wchan (symbolic names) if the absolute wchan address is nonzero" * 'core-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: fs/proc, core/debug: Don't expose absolute kernel addresses via wchan
-rw-r--r--Documentation/filesystems/proc.txt5
-rw-r--r--fs/proc/array.c16
-rw-r--r--fs/proc/base.c9
3 files changed, 20 insertions, 10 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index d411ca63c8b6..3a9d65c912e7 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -140,7 +140,8 @@ Table 1-1: Process specific entries in /proc
stat Process status
statm Process memory status information
status Process status in human readable form
- wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
+ wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
+ symbol the task is blocked in - or "0" if not blocked.
pagemap Page table
stack Report full stack trace, enable via CONFIG_STACKTRACE
smaps a extension based on maps, showing the memory consumption of
@@ -310,7 +311,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
blocked bitmap of blocked signals
sigign bitmap of ignored signals
sigcatch bitmap of caught signals
- wchan address where process went to sleep
+ 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
0 (place holder)
0 (place holder)
exit_signal signal to send to parent thread on exit
diff --git a/fs/proc/array.c b/fs/proc/array.c
index f60f0121e331..eed2050db9be 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -375,7 +375,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task, int whole)
{
- unsigned long vsize, eip, esp, wchan = ~0UL;
+ unsigned long vsize, eip, esp, wchan = 0;
int priority, nice;
int tty_pgrp = -1, tty_nr = 0;
sigset_t sigign, sigcatch;
@@ -507,7 +507,19 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL);
seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL);
seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL);
- seq_put_decimal_ull(m, ' ', wchan);
+
+ /*
+ * We used to output the absolute kernel address, but that's an
+ * information leak - so instead we show a 0/1 flag here, to signal
+ * to user-space whether there's a wchan field in /proc/PID/wchan.
+ *
+ * This works with older implementations of procps as well.
+ */
+ if (wchan)
+ seq_puts(m, " 1");
+ else
+ seq_puts(m, " 0");
+
seq_put_decimal_ull(m, ' ', 0);
seq_put_decimal_ull(m, ' ', 0);
seq_put_decimal_ll(m, ' ', task->exit_signal);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b25eee4cead5..29595af32866 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -430,13 +430,10 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
wchan = get_wchan(task);
- if (lookup_symbol_name(wchan, symname) < 0) {
- if (!ptrace_may_access(task, PTRACE_MODE_READ))
- return 0;
- seq_printf(m, "%lu", wchan);
- } else {
+ if (wchan && ptrace_may_access(task, PTRACE_MODE_READ) && !lookup_symbol_name(wchan, symname))
seq_printf(m, "%s", symname);
- }
+ else
+ seq_putc(m, '0');
return 0;
}