[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20210329075631.031062802@linuxfoundation.org>
Date: Mon, 29 Mar 2021 09:56:26 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Sergei Trofimovich <slyfox@...too.org>,
"Dmitry V. Levin" <ldv@...linux.org>,
Oleg Nesterov <oleg@...hat.com>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 055/221] ia64: fix ia64_syscall_get_set_arguments() for break-based syscalls
From: Sergei Trofimovich <slyfox@...too.org>
[ Upstream commit 0ceb1ace4a2778e34a5414e5349712ae4dc41d85 ]
In https://bugs.gentoo.org/769614 Dmitry noticed that
`ptrace(PTRACE_GET_SYSCALL_INFO)` does not work for syscalls called via
glibc's syscall() wrapper.
ia64 has two ways to call syscalls from userspace: via `break` and via
`eps` instructions.
The difference is in stack layout:
1. `eps` creates simple stack frame: no locals, in{0..7} == out{0..8}
2. `break` uses userspace stack frame: may be locals (glibc provides
one), in{0..7} == out{0..8}.
Both work fine in syscall handling cde itself.
But `ptrace(PTRACE_GET_SYSCALL_INFO)` uses unwind mechanism to
re-extract syscall arguments but it does not account for locals.
The change always skips locals registers. It should not change `eps`
path as kernel's handler already enforces locals=0 and fixes `break`.
Tested on v5.10 on rx3600 machine (ia64 9040 CPU).
Link: https://lkml.kernel.org/r/20210221002554.333076-1-slyfox@gentoo.org
Link: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@...too.org>
Reported-by: Dmitry V. Levin <ldv@...linux.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/ia64/kernel/ptrace.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 75c070aed81e..dad3a605cb7e 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -2010,27 +2010,39 @@ static void syscall_get_set_args_cb(struct unw_frame_info *info, void *data)
{
struct syscall_get_set_args *args = data;
struct pt_regs *pt = args->regs;
- unsigned long *krbs, cfm, ndirty;
+ unsigned long *krbs, cfm, ndirty, nlocals, nouts;
int i, count;
if (unw_unwind_to_user(info) < 0)
return;
+ /*
+ * We get here via a few paths:
+ * - break instruction: cfm is shared with caller.
+ * syscall args are in out= regs, locals are non-empty.
+ * - epsinstruction: cfm is set by br.call
+ * locals don't exist.
+ *
+ * For both cases argguments are reachable in cfm.sof - cfm.sol.
+ * CFM: [ ... | sor: 17..14 | sol : 13..7 | sof : 6..0 ]
+ */
cfm = pt->cr_ifs;
+ nlocals = (cfm >> 7) & 0x7f; /* aka sol */
+ nouts = (cfm & 0x7f) - nlocals; /* aka sof - sol */
krbs = (unsigned long *)info->task + IA64_RBS_OFFSET/8;
ndirty = ia64_rse_num_regs(krbs, krbs + (pt->loadrs >> 19));
count = 0;
if (in_syscall(pt))
- count = min_t(int, args->n, cfm & 0x7f);
+ count = min_t(int, args->n, nouts);
+ /* Iterate over outs. */
for (i = 0; i < count; i++) {
+ int j = ndirty + nlocals + i + args->i;
if (args->rw)
- *ia64_rse_skip_regs(krbs, ndirty + i + args->i) =
- args->args[i];
+ *ia64_rse_skip_regs(krbs, j) = args->args[i];
else
- args->args[i] = *ia64_rse_skip_regs(krbs,
- ndirty + i + args->i);
+ args->args[i] = *ia64_rse_skip_regs(krbs, j);
}
if (!args->rw) {
--
2.30.1
Powered by blists - more mailing lists