MIPS: Sanitize restart logics

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@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1698/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index 0176ed0..32103cc 100644 (file)
--- 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..73a061e 100644 (file)
--- 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, 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
 
 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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.
         */