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Message-ID: <CA+y5pbQpeUsnuzu_K+6ayzN5YFm0somg4kXqHFxFrT5g9cmQ7A@mail.gmail.com>
Date: Wed, 14 Oct 2015 22:23:59 +0100
From: "Amanieu d'Antras" <amanieu@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, x86@...nel.org,
Brian Gerst <brgerst@...il.com>,
"Amanieu d'Antras" <amanieu@...il.com>
Subject: Re: [PATCH 19/20] signalfd: Fix handling of ssi_ptr and ssi_int in signalfd_copyinfo
Sorry, this was an old version of the patch that was accidentally
sent. Please ignore it.
On Wed, Oct 14, 2015 at 9:59 PM, Amanieu d'Antras <amanieu@...il.com> wrote:
> There are several issues here:
> 1) The value of ssi_ptr was incorrect for 32-bit processes. It was
> previously copied directly from si_ptr, which contains garbage
> on 32-bit processes, especially on big-endian architectures.
>
> 2) A SIGSYS would cause various fields to be filled with incorrect
> values. SIGSYS fields are not in signalfd_siginfo, and it should
> avoid filling in unrelated fields.
>
> 3) ssi_ptr and ssi_int should not be filled in for any unrecognized
> si_code, but only for those generated by sigqueue. The si_ptr
> and si_int fields in siginfo_t may not be initialized otherwise.
>
> Signed-off-by: Amanieu d'Antras <amanieu@...il.com>
> ---
> fs/signalfd.c | 42 +++++++++++++++++++++++++++++++-----------
> 1 file changed, 31 insertions(+), 11 deletions(-)
>
> diff --git a/fs/signalfd.c b/fs/signalfd.c
> index 270221f..4d59de9 100644
> --- a/fs/signalfd.c
> +++ b/fs/signalfd.c
> @@ -80,22 +80,43 @@ static unsigned int signalfd_poll(struct file *file, poll_table *wait)
> static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> siginfo_t const *kinfo)
> {
> - long err;
> + long err, ssi_ptr;
>
> BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128);
>
> /*
> + * ssi_ptr for a compat task should be sourced from si_int instead
> + * of si_ptr since that is what copy_siginfo_from_user32 and
> + * get_compat_sigevent use. 32-bit pointer values are sign-extended
> + * to 64 bits when written to ssi_ptr, which matches the behavior of
> + * 32-bit kernels.
> + */
> + ssi_ptr = is_compat_task() ? kinfo->si_int : (long) kinfo->si_ptr;
> +
> + /*
> * Unused members should be zero ...
> */
> err = __clear_user(uinfo, sizeof(*uinfo));
>
> /*
> - * If you change siginfo_t structure, please be sure
> - * this code is fixed accordingly.
> + * If you change siginfo_t structure, please be sure that
> + * all these functions are fixed accordingly:
> + * copy_siginfo_to_user
> + * copy_siginfo_to_user32
> + * copy_siginfo_from_user32
> + * signalfd_copyinfo
> + * They should never copy any pad contained in the structure
> + * to avoid security leaks, but must copy the generic
> + * 3 ints plus the relevant union member.
> */
> err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo);
> err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno);
> err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code);
> + if (kinfo->si_code < 0) {
> + /* Write ssi_int and ssi_ptr for sigqueue()-generated signals */
> + err |= __put_user(ssi_ptr, &uinfo->ssi_ptr);
> + err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> + }
> switch (kinfo->si_code & __SI_MASK) {
> case __SI_KILL:
> err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
> @@ -104,7 +125,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> case __SI_TIMER:
> err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid);
> err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun);
> - err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
> + err |= __put_user(ssi_ptr, &uinfo->ssi_ptr);
> err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> break;
> case __SI_POLL:
> @@ -139,21 +160,20 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo,
> case __SI_MESGQ: /* But this is */
> err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
> err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
> - err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
> + err |= __put_user(ssi_ptr, &uinfo->ssi_ptr);
> err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> break;
> +#ifdef __ARCH_SIGSYS
> + case __SI_SYS: /* SIGSYS fields are not in signalfd_siginfo */
> + break;
> +#endif
> default:
> - /*
> - * This case catches also the signals queued by sigqueue().
> - */
> err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid);
> err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid);
> - err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr);
> - err |= __put_user(kinfo->si_int, &uinfo->ssi_int);
> break;
> }
>
> - return err ? -EFAULT: sizeof(*uinfo);
> + return err ? -EFAULT : sizeof(*uinfo);
> }
>
> static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info,
> --
> 2.6.1
>
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