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fix infoleak in waitid(2) 

kernel_waitid() can return a PID, an error or 0.  rusage is filled in the first
case and waitid(2) rusage should've been copied out exactly in that case, *not*
whenever kernel_waitid() has not returned an error.  Compat variant shares that
braino; none of kernel_wait4() callers do, so the below ought to fix it.

Reported-and-tested-by: Alexander Potapenko <glider@google.com>
Fixes: ce72a16fa7 ("wait4(2)/waitid(2): separate copying rusage to userland")
Cc: stable@vger.kernel.org # v4.13
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2017-09-29 13:43:15 -04:00
parent b776e4b1a9
commit 6c85501f2f
1 changed files with 10 additions and 13 deletions
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9
kernel/exit.c
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@ -1600,12 +1600,10 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
struct waitid_info info = {.status = 0};
long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
int signo = 0;
if (err > 0) {
signo = SIGCHLD;
err = 0;
}
if (!err) {
if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
return -EFAULT;
}
@ -1723,9 +1721,7 @@ COMPAT_SYSCALL_DEFINE5(waitid,
if (err > 0) {
signo = SIGCHLD;
err = 0;
}
if (!err && uru) {
if (uru) {
/* kernel_waitid() overwrites everything in ru */
if (COMPAT_USE_64BIT_TIME)
err = copy_to_user(uru, &ru, sizeof(ru));
@ -1734,6 +1730,7 @@ COMPAT_SYSCALL_DEFINE5(waitid,
if (err)
return -EFAULT;
}
}
if (!infop)
return err;