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proc: check permissions earlier for /proc/*/wchan

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get_wchan() accesses stack page before permissions are checked, let's
not play this game.

Link: http://lkml.kernel.org/r/20180217071923.GA16074@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2018-04-10 16:31:30 -07:00 committed by Linus Torvalds
parent d0f0223122
commit 24b2ec2119
1 changed files with 8 additions and 5 deletions
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13
fs/proc/base.c
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@ -388,14 +388,17 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
unsigned long wchan;
char symname[KSYM_NAME_LEN];
if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto print0;
wchan = get_wchan(task);
if (wchan && ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)
&& !lookup_symbol_name(wchan, symname))
if (wchan && !lookup_symbol_name(wchan, symname)) {
seq_printf(m, "%s", symname);
else
seq_putc(m, '0');
return 0;
}
print0:
seq_putc(m, '0');
return 0;
}
#endif /* CONFIG_KALLSYMS */