kvm: Use 'unsigned long' for request argument in functions wrapping ioctl()

Change the data type of the ioctl _request_ argument from 'int' to
'unsigned long' for the various accel/kvm functions which are
essentially wrappers around the ioctl() syscall.

The correct type for ioctl()'s 'request' argument is confused:
 * POSIX defines the request argument as 'int'
 * glibc uses 'unsigned long' in the prototype in sys/ioctl.h
 * the glibc info documentation uses 'int'
 * the Linux manpage uses 'unsigned long'
 * the Linux implementation of the syscall uses 'unsigned int'

If we wrap ioctl() with another function which uses 'int' as the
type for the request argument, then requests with the 0x8000_0000
bit set will be sign-extended when the 'int' is cast to
'unsigned long' for the call to ioctl().

On x86_64 one such example is the KVM_IRQ_LINE_STATUS request.
Bit requests with the _IOC_READ direction bit set, will have the high
bit set.

Fortunately the Linux Kernel truncates the upper 32bit of the request
on 64bit machines (because it uses 'unsigned int', and see also Linus
Torvalds' comments in
  https://sourceware.org/bugzilla/show_bug.cgi?id=14362 )
so this doesn't cause active problems for us.  However it is more
consistent to follow the glibc ioctl() prototype when we define
functions that are essentially wrappers around ioctl().

This resolves a Coverity issue where it points out that in
kvm_get_xsave() we assign a value (KVM_GET_XSAVE or KVM_GET_XSAVE2)
to an 'int' variable which can't hold it without overflow.

Resolves: Coverity CID 1547759
Signed-off-by: Johannes Stoelp <johannes.stoelp@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20240815122747.3053871-1-peter.maydell@linaro.org
[PMM: Rebased patch, adjusted commit message, included note about
 Coverity fix, updated the type of the local var in kvm_get_xsave,
 updated the comment in the KVMState struct definition]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 75d11a07b2bcebf32f6ac06ffd7c99ad7f1d179b..beb1988d12cf4c77bc9bf02c7396f8c268735c9f 100644 (file)
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -3170,7 +3170,7 @@ int kvm_cpu_exec(CPUState *cpu)
     return ret;
 }
 
-int kvm_ioctl(KVMState *s, int type, ...)
+int kvm_ioctl(KVMState *s, unsigned long type, ...)
 {
     int ret;
     void *arg;
@@ -3188,7 +3188,7 @@ int kvm_ioctl(KVMState *s, int type, ...)
     return ret;
 }
 
-int kvm_vm_ioctl(KVMState *s, int type, ...)
+int kvm_vm_ioctl(KVMState *s, unsigned long type, ...)
 {
     int ret;
     void *arg;
@@ -3208,7 +3208,7 @@ int kvm_vm_ioctl(KVMState *s, int type, ...)
     return ret;
 }
 
-int kvm_vcpu_ioctl(CPUState *cpu, int type, ...)
+int kvm_vcpu_ioctl(CPUState *cpu, unsigned long type, ...)
 {
     int ret;
     void *arg;
@@ -3228,7 +3228,7 @@ int kvm_vcpu_ioctl(CPUState *cpu, int type, ...)
     return ret;
 }
 
-int kvm_device_ioctl(int fd, int type, ...)
+int kvm_device_ioctl(int fd, unsigned long type, ...)
 {
     int ret;
     void *arg;

diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events
index 37626c1ac5d0fc860cdf0d5bb1ca5e7b440b8281..82c65fd2ab882731331831c82b2660c360c7f914 100644 (file)
--- a/accel/kvm/trace-events
+++ b/accel/kvm/trace-events
@@ -1,11 +1,11 @@
 # See docs/devel/tracing.rst for syntax documentation.
 
 # kvm-all.c
-kvm_ioctl(int type, void *arg) "type 0x%x, arg %p"
-kvm_vm_ioctl(int type, void *arg) "type 0x%x, arg %p"
-kvm_vcpu_ioctl(int cpu_index, int type, void *arg) "cpu_index %d, type 0x%x, arg %p"
+kvm_ioctl(unsigned long type, void *arg) "type 0x%lx, arg %p"
+kvm_vm_ioctl(unsigned long type, void *arg) "type 0x%lx, arg %p"
+kvm_vcpu_ioctl(int cpu_index, unsigned long type, void *arg) "cpu_index %d, type 0x%lx, arg %p"
 kvm_run_exit(int cpu_index, uint32_t reason) "cpu_index %d, reason %d"
-kvm_device_ioctl(int fd, int type, void *arg) "dev fd %d, type 0x%x, arg %p"
+kvm_device_ioctl(int fd, unsigned long type, void *arg) "dev fd %d, type 0x%lx, arg %p"
 kvm_failed_reg_get(uint64_t id, const char *msg) "Warning: Unable to retrieve ONEREG %" PRIu64 " from KVM: %s"
 kvm_failed_reg_set(uint64_t id, const char *msg) "Warning: Unable to set ONEREG %" PRIu64 " to KVM: %s"
 kvm_init_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 9cf14ca3d5b37fa0be6a734c6bfd17e3266c0c68..613d3f7581fe7dbb20a22688d787e065371fd298 100644 (file)
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -235,11 +235,11 @@ static inline int kvm_update_guest_debug(CPUState *cpu, unsigned long reinject_t
 
 /* internal API */
 
-int kvm_ioctl(KVMState *s, int type, ...);
+int kvm_ioctl(KVMState *s, unsigned long type, ...);
 
-int kvm_vm_ioctl(KVMState *s, int type, ...);
+int kvm_vm_ioctl(KVMState *s, unsigned long type, ...);
 
-int kvm_vcpu_ioctl(CPUState *cpu, int type, ...);
+int kvm_vcpu_ioctl(CPUState *cpu, unsigned long type, ...);
 
 /**
  * kvm_device_ioctl - call an ioctl on a kvm device
@@ -248,7 +248,7 @@ int kvm_vcpu_ioctl(CPUState *cpu, int type, ...);
  *
  * Returns: -errno on error, nonnegative on success
  */
-int kvm_device_ioctl(int fd, int type, ...);
+int kvm_device_ioctl(int fd, unsigned long type, ...);
 
 /**
  * kvm_vm_check_attr - check for existence of a specific vm attribute

diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
index 1d8fb1473bdfc7c047c8f4a95636bd84f82de8dd..17483ff53bd2cf8c8158dcf4a36e2a429f03a837 100644 (file)
--- a/include/sysemu/kvm_int.h
+++ b/include/sysemu/kvm_int.h
@@ -122,10 +122,19 @@ struct KVMState
     bool sync_mmu;
     bool guest_state_protected;
     uint64_t manual_dirty_log_protect;
-    /* The man page (and posix) say ioctl numbers are signed int, but
-     * they're not.  Linux, glibc and *BSD all treat ioctl numbers as
-     * unsigned, and treating them as signed here can break things */
-    unsigned irq_set_ioctl;
+    /*
+     * Older POSIX says that ioctl numbers are signed int, but in
+     * practice they are not. (Newer POSIX doesn't specify ioctl
+     * at all.) Linux, glibc and *BSD all treat ioctl numbers as
+     * unsigned, and real-world ioctl values like KVM_GET_XSAVE have
+     * bit 31 set, which means that passing them via an 'int' will
+     * result in sign-extension when they get converted back to the
+     * 'unsigned long' which the ioctl() prototype uses. Luckily Linux
+     * always treats the argument as an unsigned 32-bit int, so any
+     * possible sign-extension is deliberately ignored, but for
+     * consistency we keep to the same type that glibc is using.
+     */
+    unsigned long irq_set_ioctl;
     unsigned int sigmask_len;
     GHashTable *gsimap;
 #ifdef KVM_CAP_IRQ_ROUTING

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 2fa88ef1e373d44be5afb13305f6e1ddcfb64244..ada581c5d6eaddcc7c828c68d383406c60106ecc 100644 (file)
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -4102,7 +4102,8 @@ static int kvm_get_xsave(X86CPU *cpu)
 {
     CPUX86State *env = &cpu->env;
     void *xsave = env->xsave_buf;
-    int type, ret;
+    unsigned long type;
+    int ret;
 
     type = has_xsave2 ? KVM_GET_XSAVE2 : KVM_GET_XSAVE;
     ret = kvm_vcpu_ioctl(CPU(cpu), type, xsave);