[PATCH 3/5] mips: sanitize restart logics

From: Al Viro
Date: Tue Sep 28 2010 - 13:50:44 EST


Put the original syscall number into ->regs[0] when we leave syscall
with error. Use it in restart logics. Everything else will have
it 0 since we pass through SAVE_SOME on all the ways in. Note that
in places like bad_stack and inllegal_syscall we leave it 0 - it's
not restartable.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
arch/mips/kernel/branch.c | 1 -
arch/mips/kernel/scall32-o32.S | 9 ++++-----
arch/mips/kernel/scall64-64.S | 7 ++++---
arch/mips/kernel/scall64-n32.S | 6 ++++--
arch/mips/kernel/scall64-o32.S | 7 ++++---
arch/mips/kernel/signal.c | 37 ++++++++++++++++++-------------------
arch/mips/kernel/unaligned.c | 2 --
7 files changed, 34 insertions(+), 35 deletions(-)

diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index 0176ed0..32103cc 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -40,7 +40,6 @@ int __compute_return_epc(struct pt_regs *regs)
return -EFAULT;
}

- regs->regs[0] = 0;
switch (insn.i_format.opcode) {
/*
* jr and jalr are in r_format format.
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index 17202bb..d3edb9f 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -63,9 +63,9 @@ stack_done:
sw t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ lw t1, PR_R2(sp) # syscall number
negu v0 # error
- sw v0, PT_R0(sp) # set flag for syscall
- # restarting
+ sw t1, PT_R0(sp) # save it for syscall restarting
1: sw v0, PT_R2(sp) # result

o32_syscall_exit:
@@ -104,9 +104,9 @@ syscall_trace_entry:
sw t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ lw t1, PT_R2(sp) # syscall number
negu v0 # error
- sw v0, PT_R0(sp) # set flag for syscall
- # restarting
+ sw t1, PT_R0(sp) # save it for syscall restarting
1: sw v0, PT_R2(sp) # result

j syscall_exit
@@ -170,7 +170,6 @@ stackargs:
*/
bad_stack:
negu v0 # error
- sw v0, PT_R0(sp)
sw v0, PT_R2(sp)
li t0, 1 # set error flag
sw t0, PT_R7(sp)
diff --git a/arch/mips/kernel/scall64-64.S b/arch/mips/kernel/scall64-64.S
index a8a6c59..eb0bb73 100644
--- a/arch/mips/kernel/scall64-64.S
+++ b/arch/mips/kernel/scall64-64.S
@@ -66,9 +66,9 @@ NESTED(handle_sys64, PT_SIZE, sp)
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # set flag for syscall
- # restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

n64_syscall_exit:
@@ -109,8 +109,9 @@ syscall_trace_entry:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # set flag for syscall restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

j syscall_exit
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index a3d6613..4da3faf 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -65,8 +65,9 @@ NESTED(handle_sysn32, PT_SIZE, sp)
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # set flag for syscall restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

local_irq_disable # make sure need_resched and
@@ -106,8 +107,9 @@ n32_syscall_trace_entry:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # set flag for syscall restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

j syscall_exit
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index 813689e..7ce0a36 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -93,8 +93,9 @@ NESTED(handle_sys, PT_SIZE, sp)
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # flag for syscall restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

o32_syscall_exit:
@@ -142,8 +143,9 @@ trace_a_syscall:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f

+ ld t1, PT_R2(sp) # syscall number
dnegu v0 # error
- sd v0, PT_R0(sp) # set flag for syscall restarting
+ sd t1, PT_R0(sp) # save it for syscall restarting
1: sd v0, PT_R2(sp) # result

j syscall_exit
@@ -155,7 +157,6 @@ trace_a_syscall:
*/
bad_stack:
dnegu v0 # error
- sd v0, PT_R0(sp)
sd v0, PT_R2(sp)
li t0, 1 # set error flag
sd t0, PT_R7(sp)
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index b3273ae..604f077 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -550,23 +550,26 @@ static int handle_signal(unsigned long sig, siginfo_t *info,
struct mips_abi *abi = current->thread.abi;
void *vdso = current->mm->context.vdso;

- switch(regs->regs[0]) {
- case ERESTART_RESTARTBLOCK:
- case ERESTARTNOHAND:
- regs->regs[2] = EINTR;
- break;
- case ERESTARTSYS:
- if (!(ka->sa.sa_flags & SA_RESTART)) {
+ if (regs->regs[0]) {
+ switch(regs->regs[2]) {
+ case ERESTART_RESTARTBLOCK:
+ case ERESTARTNOHAND:
regs->regs[2] = EINTR;
break;
+ case ERESTARTSYS:
+ if (!(ka->sa.sa_flags & SA_RESTART)) {
+ regs->regs[2] = EINTR;
+ break;
+ }
+ /* fallthrough */
+ case ERESTARTNOINTR:
+ regs->regs[7] = regs->regs[26];
+ regs->regs[2] = regs->regs[0];
+ regs->cp0_epc -= 4;
}
- /* fallthrough */
- case ERESTARTNOINTR: /* Userland will reload $v0. */
- regs->regs[7] = regs->regs[26];
- regs->cp0_epc -= 8;
- }

- regs->regs[0] = 0; /* Don't deal with this again. */
+ regs->regs[0] = 0; /* Don't deal with this again. */
+ }

if (sig_uses_siginfo(ka))
ret = abi->setup_rt_frame(vdso + abi->rt_signal_return_offset,
@@ -625,17 +628,13 @@ static void do_signal(struct pt_regs *regs)
return;
}

- /*
- * Who's code doesn't conform to the restartable syscall convention
- * dies here!!! The li instruction, a single machine instruction,
- * must directly be followed by the syscall instruction.
- */
if (regs->regs[0]) {
if (regs->regs[2] == ERESTARTNOHAND ||
regs->regs[2] == ERESTARTSYS ||
regs->regs[2] == ERESTARTNOINTR) {
+ regs->regs[2] = regs->regs[0];
regs->regs[7] = regs->regs[26];
- regs->cp0_epc -= 8;
+ regs->cp0_epc -= 4;
}
if (regs->regs[2] == ERESTART_RESTARTBLOCK) {
regs->regs[2] = current->thread.abi->restart;
diff --git a/arch/mips/kernel/unaligned.c b/arch/mips/kernel/unaligned.c
index 69b039c..33d5a5c 100644
--- a/arch/mips/kernel/unaligned.c
+++ b/arch/mips/kernel/unaligned.c
@@ -109,8 +109,6 @@ static void emulate_load_store_insn(struct pt_regs *regs,
unsigned long value;
unsigned int res;

- regs->regs[0] = 0;
-
/*
* This load never faults.
*/
--
1.5.6.5


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