[Qemu-devel] [PATCH v2] linux-user: Simplify timerid checks on g_posix_timers range

[Alexander Graf]

We check whether the passed in timer id is negative on all calls
that involve g_posix_timers.

However, these checks are bogus. First off we limit the timer_id to
16 bits which is not what Linux does. Then we check whether it's negative
which it can't be because we masked it.

We can safely remove the masking. For the negativity check we can just
treat the timerid as unsigned and only check for upper boundaries.

Signed-off-by: Alexander Graf <address@hidden>

---

v1 -> v2:

  - drop 0xffff mask
  - explicitly cast to unsigned because the mask is missing now

---
 linux-user/syscall.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f6c887f..92b6a38 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9508,11 +9508,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
     {
         /* args: timer_t timerid, int flags, const struct itimerspec 
*new_value,
          * struct itimerspec * old_value */
-        arg1 &= 0xffff;
-        if (arg3 == 0 || arg1 < 0 || arg1 >= ARRAY_SIZE(g_posix_timers)) {
+        target_ulong timerid = arg1;
+
+        if (arg3 == 0 || timerid >= ARRAY_SIZE(g_posix_timers)) {
             ret = -TARGET_EINVAL;
         } else {
-            timer_t htimer = g_posix_timers[arg1];
+            timer_t htimer = g_posix_timers[timerid];
             struct itimerspec hspec_new = {{0},}, hspec_old = {{0},};
 
             target_to_host_itimerspec(&hspec_new, arg3);
@@ -9528,13 +9529,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
     case TARGET_NR_timer_gettime:
     {
         /* args: timer_t timerid, struct itimerspec *curr_value */
-        arg1 &= 0xffff;
+        target_ulong timerid = arg1;
+
         if (!arg2) {
             return -TARGET_EFAULT;
-        } else if (arg1 < 0 || arg1 >= ARRAY_SIZE(g_posix_timers)) {
+        } else if (timerid >= ARRAY_SIZE(g_posix_timers)) {
             ret = -TARGET_EINVAL;
         } else {
-            timer_t htimer = g_posix_timers[arg1];
+            timer_t htimer = g_posix_timers[timerid];
             struct itimerspec hspec;
             ret = get_errno(timer_gettime(htimer, &hspec));
 
@@ -9550,11 +9552,12 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
     case TARGET_NR_timer_getoverrun:
     {
         /* args: timer_t timerid */
-        arg1 &= 0xffff;
-        if (arg1 < 0 || arg1 >= ARRAY_SIZE(g_posix_timers)) {
+        target_ulong timerid = arg1;
+
+        if (timerid >= ARRAY_SIZE(g_posix_timers)) {
             ret = -TARGET_EINVAL;
         } else {
-            timer_t htimer = g_posix_timers[arg1];
+            timer_t htimer = g_posix_timers[timerid];
             ret = get_errno(timer_getoverrun(htimer));
         }
         break;
@@ -9565,13 +9568,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
     case TARGET_NR_timer_delete:
     {
         /* args: timer_t timerid */
-        arg1 &= 0xffff;
-        if (arg1 < 0 || arg1 >= ARRAY_SIZE(g_posix_timers)) {
+        target_ulong timerid = arg1;
+
+        if (timerid >= ARRAY_SIZE(g_posix_timers)) {
             ret = -TARGET_EINVAL;
         } else {
-            timer_t htimer = g_posix_timers[arg1];
+            timer_t htimer = g_posix_timers[timerid];
             ret = get_errno(timer_delete(htimer));
-            g_posix_timers[arg1] = 0;
+            g_posix_timers[timerid] = 0;
         }
         break;
     }
-- 
1.7.12.4