* [PATCH] fix undefined behavior in ptrace
@ 2017-06-28 13:25 Alexander Monakov
2017-06-28 15:13 ` Rich Felker
0 siblings, 1 reply; 6+ messages in thread
From: Alexander Monakov @ 2017-06-28 13:25 UTC (permalink / raw)
To: musl
---
src/linux/ptrace.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/linux/ptrace.c b/src/linux/ptrace.c
index 83b8022b..ab7fcda3 100644
--- a/src/linux/ptrace.c
+++ b/src/linux/ptrace.c
@@ -7,14 +7,17 @@ long ptrace(int req, ...)
{
va_list ap;
pid_t pid;
- void *addr, *data, *addr2;
+ void *addr, *data, *addr2 = 0;
long ret, result;
va_start(ap, req);
pid = va_arg(ap, pid_t);
addr = va_arg(ap, void *);
data = va_arg(ap, void *);
+ /* PTRACE_{READ,WRITE}{DATA,TEXT} are specific to SPARC. */
+#ifdef PTRACE_READTEXT
addr2 = va_arg(ap, void *);
+#endif
va_end(ap);
if (req-1U < 3) data = &result;
--
2.11.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fix undefined behavior in ptrace
2017-06-28 13:25 [PATCH] fix undefined behavior in ptrace Alexander Monakov
@ 2017-06-28 15:13 ` Rich Felker
2017-06-28 15:22 ` Alexander Monakov
0 siblings, 1 reply; 6+ messages in thread
From: Rich Felker @ 2017-06-28 15:13 UTC (permalink / raw)
To: musl
On Wed, Jun 28, 2017 at 04:25:13PM +0300, Alexander Monakov wrote:
> ---
> src/linux/ptrace.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/src/linux/ptrace.c b/src/linux/ptrace.c
> index 83b8022b..ab7fcda3 100644
> --- a/src/linux/ptrace.c
> +++ b/src/linux/ptrace.c
> @@ -7,14 +7,17 @@ long ptrace(int req, ...)
> {
> va_list ap;
> pid_t pid;
> - void *addr, *data, *addr2;
> + void *addr, *data, *addr2 = 0;
> long ret, result;
>
> va_start(ap, req);
> pid = va_arg(ap, pid_t);
> addr = va_arg(ap, void *);
> data = va_arg(ap, void *);
> + /* PTRACE_{READ,WRITE}{DATA,TEXT} are specific to SPARC. */
> +#ifdef PTRACE_READTEXT
> addr2 = va_arg(ap, void *);
> +#endif
I think there's still UB here, reading more args than were passed.
These calls to va_arg should probably be dependent on the particular
req; I don't see any reason for it to be compile-time dependent on the
presence of one particular req value.
Otherwise yes it's an improvement.
Rich
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fix undefined behavior in ptrace
2017-06-28 15:13 ` Rich Felker
@ 2017-06-28 15:22 ` Alexander Monakov
2017-07-04 21:10 ` Rich Felker
0 siblings, 1 reply; 6+ messages in thread
From: Alexander Monakov @ 2017-06-28 15:22 UTC (permalink / raw)
To: musl
On Wed, 28 Jun 2017, Rich Felker wrote:
> I think there's still UB here, reading more args than were passed.
> These calls to va_arg should probably be dependent on the particular
> req; I don't see any reason for it to be compile-time dependent on the
> presence of one particular req value.
I raised that last year but there was no response:
http://www.openwall.com/lists/musl/2016/05/04/18
Alexander
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fix undefined behavior in ptrace
2017-06-28 15:22 ` Alexander Monakov
@ 2017-07-04 21:10 ` Rich Felker
2017-07-04 21:51 ` Alexander Monakov
0 siblings, 1 reply; 6+ messages in thread
From: Rich Felker @ 2017-07-04 21:10 UTC (permalink / raw)
To: musl
On Wed, Jun 28, 2017 at 06:22:12PM +0300, Alexander Monakov wrote:
> On Wed, 28 Jun 2017, Rich Felker wrote:
> > I think there's still UB here, reading more args than were passed.
> > These calls to va_arg should probably be dependent on the particular
> > req; I don't see any reason for it to be compile-time dependent on the
> > presence of one particular req value.
>
> I raised that last year but there was no response:
> http://www.openwall.com/lists/musl/2016/05/04/18
I'm sorry for overlooking it then. Could you submit a fleshed-out
patch that uses that approach? Assuming the arg types are always the
same, and only the number of args varies by command, a nicer approach
than nested if's with a bunch of equality comparisons each might be a
switch statement to map commands to # of args, then
if (nargs>=1) pid = va_arg(ap, pid_t);
if (nargs>=2) addr = va_arg(ap, void *);
...
Thoughts?
Rich
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fix undefined behavior in ptrace
2017-07-04 21:10 ` Rich Felker
@ 2017-07-04 21:51 ` Alexander Monakov
2017-07-04 21:53 ` Rich Felker
0 siblings, 1 reply; 6+ messages in thread
From: Alexander Monakov @ 2017-07-04 21:51 UTC (permalink / raw)
To: musl
---
On Tue, 4 Jul 2017, Rich Felker wrote:
> Thoughts?
I'm not convinced it's a good idea, given that it's a Linux specific interface,
and the manpage rather explicitly discourages passing fewer than four
arguments.
Plus, handling SPARC-specific differences of argument counts for
PTRACE_{GET,SET}{FP,}REGS would be annoying.
What makes sense is to retrieve the fifth argument only when needed:
src/linux/ptrace.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/linux/ptrace.c b/src/linux/ptrace.c
index 83b8022b..a3f393d9 100644
--- a/src/linux/ptrace.c
+++ b/src/linux/ptrace.c
@@ -7,14 +7,18 @@ long ptrace(int req, ...)
{
va_list ap;
pid_t pid;
- void *addr, *data, *addr2;
+ void *addr, *data, *addr2 = 0;
long ret, result;
va_start(ap, req);
pid = va_arg(ap, pid_t);
addr = va_arg(ap, void *);
data = va_arg(ap, void *);
- addr2 = va_arg(ap, void *);
+ /* PTRACE_{READ,WRITE}{DATA,TEXT} (16...19) are specific to SPARC. */
+#ifdef PTRACE_READDATA
+ if ((unsigned)req - PTRACE_READDATA < 4)
+ addr2 = va_arg(ap, void *);
+#endif
va_end(ap);
if (req-1U < 3) data = &result;
--
2.11.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fix undefined behavior in ptrace
2017-07-04 21:51 ` Alexander Monakov
@ 2017-07-04 21:53 ` Rich Felker
0 siblings, 0 replies; 6+ messages in thread
From: Rich Felker @ 2017-07-04 21:53 UTC (permalink / raw)
To: musl
On Wed, Jul 05, 2017 at 12:51:05AM +0300, Alexander Monakov wrote:
> ---
> On Tue, 4 Jul 2017, Rich Felker wrote:
> > Thoughts?
>
> I'm not convinced it's a good idea, given that it's a Linux specific interface,
> and the manpage rather explicitly discourages passing fewer than four
> arguments.
>
> Plus, handling SPARC-specific differences of argument counts for
> PTRACE_{GET,SET}{FP,}REGS would be annoying.
>
> What makes sense is to retrieve the fifth argument only when needed:
Ah, okay. I'm fine with that. Thanks for clarifying.
> src/linux/ptrace.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/src/linux/ptrace.c b/src/linux/ptrace.c
> index 83b8022b..a3f393d9 100644
> --- a/src/linux/ptrace.c
> +++ b/src/linux/ptrace.c
> @@ -7,14 +7,18 @@ long ptrace(int req, ...)
> {
> va_list ap;
> pid_t pid;
> - void *addr, *data, *addr2;
> + void *addr, *data, *addr2 = 0;
> long ret, result;
>
> va_start(ap, req);
> pid = va_arg(ap, pid_t);
> addr = va_arg(ap, void *);
> data = va_arg(ap, void *);
> - addr2 = va_arg(ap, void *);
> + /* PTRACE_{READ,WRITE}{DATA,TEXT} (16...19) are specific to SPARC. */
> +#ifdef PTRACE_READDATA
> + if ((unsigned)req - PTRACE_READDATA < 4)
> + addr2 = va_arg(ap, void *);
> +#endif
> va_end(ap);
>
> if (req-1U < 3) data = &result;
> --
> 2.11.0
Applying.
Rich
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-07-04 21:53 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2017-06-28 13:25 [PATCH] fix undefined behavior in ptrace Alexander Monakov
2017-06-28 15:13 ` Rich Felker
2017-06-28 15:22 ` Alexander Monakov
2017-07-04 21:10 ` Rich Felker
2017-07-04 21:51 ` Alexander Monakov
2017-07-04 21:53 ` Rich Felker
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