Blob Blame Raw
From 6dd1f60e226cb3c8ad0791dd6c8edba2493145cd Mon Sep 17 00:00:00 2001
From: Cornelia Huck <cohuck@redhat.com>
Date: Wed, 17 Apr 2019 13:57:19 +0100
Subject: [PATCH 02/24] loader: Check access size when calling rom_ptr() to
 avoid crashes

RH-Author: Cornelia Huck <cohuck@redhat.com>
Message-id: <20190417135741.25297-3-cohuck@redhat.com>
Patchwork-id: 85785
O-Subject: [RHEL-8.1.0 qemu-kvm PATCH v2 02/24] loader: Check access size when calling rom_ptr() to avoid crashes
Bugzilla: 1699070
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>
RH-Acked-by: Jens Freimann <jfreimann@redhat.com>

From: Thomas Huth <thuth@redhat.com>

The rom_ptr() function allows direct access to the ROM blobs that we
load during startup. However, there are currently no checks for the
size of the accesses, so it's currently possible to crash QEMU for
example with:

$ echo "Insane in the mainframe" > /tmp/test.txt
$ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -append xyz
Segmentation fault (core dumped)
$ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -initrd /tmp/test.txt
Segmentation fault (core dumped)
$ echo -n HdrS > /tmp/hdr.txt
$ sparc64-softmmu/qemu-system-sparc64 -kernel /tmp/hdr.txt -initrd /tmp/hdr.txt
Segmentation fault (core dumped)

We need a possibility to check the size of the ROM area that we want
to access, thus let's add a size parameter to the rom_ptr() function
to avoid these problems.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1530005740-25254-1-git-send-email-thuth@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
(cherry picked from commit 0f0f8b611eeea663c8d3b6021918033e257411a1)
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 hw/core/loader.c     | 10 +++++-----
 hw/mips/mips_malta.c |  6 ++++--
 hw/s390x/ipl.c       | 18 ++++++++++++------
 hw/sparc/sun4m.c     |  4 ++--
 hw/sparc64/sun4u.c   |  4 ++--
 include/hw/loader.h  |  2 +-
 target/arm/cpu.c     |  2 +-
 7 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 06bdbca..bbb6e65 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -191,7 +191,7 @@ void pstrcpy_targphys(const char *name, hwaddr dest, int buf_size,
         rom_add_blob_fixed(name, source, (nulp - source) + 1, dest);
     } else {
         rom_add_blob_fixed(name, source, buf_size, dest);
-        ptr = rom_ptr(dest + buf_size - 1);
+        ptr = rom_ptr(dest + buf_size - 1, sizeof(*ptr));
         *ptr = 0;
     }
 }
@@ -1165,7 +1165,7 @@ void rom_reset_order_override(void)
     fw_cfg_reset_order_override(fw_cfg);
 }
 
-static Rom *find_rom(hwaddr addr)
+static Rom *find_rom(hwaddr addr, size_t size)
 {
     Rom *rom;
 
@@ -1179,7 +1179,7 @@ static Rom *find_rom(hwaddr addr)
         if (rom->addr > addr) {
             continue;
         }
-        if (rom->addr + rom->romsize < addr) {
+        if (rom->addr + rom->romsize < addr + size) {
             continue;
         }
         return rom;
@@ -1249,11 +1249,11 @@ int rom_copy(uint8_t *dest, hwaddr addr, size_t size)
     return (d + l) - dest;
 }
 
-void *rom_ptr(hwaddr addr)
+void *rom_ptr(hwaddr addr, size_t size)
 {
     Rom *rom;
 
-    rom = find_rom(addr);
+    rom = find_rom(addr, size);
     if (!rom || !rom->data)
         return NULL;
     return rom->data + (addr - rom->addr);
diff --git a/hw/mips/mips_malta.c b/hw/mips/mips_malta.c
index f6513a4..8bbea0b 100644
--- a/hw/mips/mips_malta.c
+++ b/hw/mips/mips_malta.c
@@ -1139,11 +1139,13 @@ void mips_malta_init(MachineState *machine)
            a neat trick which allows bi-endian firmware. */
 #ifndef TARGET_WORDS_BIGENDIAN
         {
-            uint32_t *end, *addr = rom_ptr(FLASH_ADDRESS);
+            uint32_t *end, *addr;
+            const size_t swapsize = MIN(bios_size, 0x3e0000);
+            addr = rom_ptr(FLASH_ADDRESS, swapsize);
             if (!addr) {
                 addr = memory_region_get_ram_ptr(bios);
             }
-            end = (void *)addr + MIN(bios_size, 0x3e0000);
+            end = (void *)addr + swapsize;
             while (addr < end) {
                 bswap32s(addr);
                 addr++;
diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 617ac43..10038ec 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -32,7 +32,6 @@
 #define KERN_PARM_AREA                  0x010480UL
 #define INITRD_START                    0x800000UL
 #define INITRD_PARM_START               0x010408UL
-#define INITRD_PARM_SIZE                0x010410UL
 #define PARMFILE_START                  0x001000UL
 #define ZIPL_IMAGE_START                0x009000UL
 #define IPL_PSW_MASK                    (PSW_MASK_32 | PSW_MASK_64)
@@ -164,12 +163,12 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
                 goto error;
             }
             /* if this is Linux use KERN_IMAGE_START */
-            magic = rom_ptr(LINUX_MAGIC_ADDR);
+            magic = rom_ptr(LINUX_MAGIC_ADDR, 6);
             if (magic && !memcmp(magic, "S390EP", 6)) {
                 pentry = KERN_IMAGE_START;
             } else {
                 /* if not Linux load the address of the (short) IPL PSW */
-                ipl_psw = rom_ptr(4);
+                ipl_psw = rom_ptr(4, 4);
                 if (ipl_psw) {
                     pentry = be32_to_cpu(*ipl_psw) & 0x7fffffffUL;
                 } else {
@@ -185,9 +184,12 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
          * loader) and it won't work. For this case we force it to 0x10000, too.
          */
         if (pentry == KERN_IMAGE_START || pentry == 0x800) {
+            char *parm_area = rom_ptr(KERN_PARM_AREA, strlen(ipl->cmdline) + 1);
             ipl->start_addr = KERN_IMAGE_START;
             /* Overwrite parameters in the kernel image, which are "rom" */
-            strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline);
+            if (parm_area) {
+                strcpy(parm_area, ipl->cmdline);
+            }
         } else {
             ipl->start_addr = pentry;
         }
@@ -195,6 +197,7 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
         if (ipl->initrd) {
             ram_addr_t initrd_offset;
             int initrd_size;
+            uint64_t *romptr;
 
             initrd_offset = INITRD_START;
             while (kernel_size + 0x100000 > initrd_offset) {
@@ -211,8 +214,11 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
              * we have to overwrite values in the kernel image,
              * which are "rom"
              */
-            stq_p(rom_ptr(INITRD_PARM_START), initrd_offset);
-            stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size);
+            romptr = rom_ptr(INITRD_PARM_START, 16);
+            if (romptr) {
+                stq_p(romptr, initrd_offset);
+                stq_p(romptr + 1, initrd_size);
+            }
         }
     }
     /*
diff --git a/hw/sparc/sun4m.c b/hw/sparc/sun4m.c
index 6471aca..a400442 100644
--- a/hw/sparc/sun4m.c
+++ b/hw/sparc/sun4m.c
@@ -272,8 +272,8 @@ static unsigned long sun4m_load_kernel(const char *kernel_filename,
         }
         if (initrd_size > 0) {
             for (i = 0; i < 64 * TARGET_PAGE_SIZE; i += TARGET_PAGE_SIZE) {
-                ptr = rom_ptr(KERNEL_LOAD_ADDR + i);
-                if (ldl_p(ptr) == 0x48647253) { // HdrS
+                ptr = rom_ptr(KERNEL_LOAD_ADDR + i, 24);
+                if (ptr && ldl_p(ptr) == 0x48647253) { /* HdrS */
                     stl_p(ptr + 16, INITRD_LOAD_ADDR);
                     stl_p(ptr + 20, initrd_size);
                     break;
diff --git a/hw/sparc64/sun4u.c b/hw/sparc64/sun4u.c
index 2044a52..1410c3a 100644
--- a/hw/sparc64/sun4u.c
+++ b/hw/sparc64/sun4u.c
@@ -186,8 +186,8 @@ static uint64_t sun4u_load_kernel(const char *kernel_filename,
         }
         if (*initrd_size > 0) {
             for (i = 0; i < 64 * TARGET_PAGE_SIZE; i += TARGET_PAGE_SIZE) {
-                ptr = rom_ptr(*kernel_addr + i);
-                if (ldl_p(ptr + 8) == 0x48647253) { /* HdrS */
+                ptr = rom_ptr(*kernel_addr + i, 32);
+                if (ptr && ldl_p(ptr + 8) == 0x48647253) { /* HdrS */
                     stl_p(ptr + 24, *initrd_addr + *kernel_addr);
                     stl_p(ptr + 28, *initrd_size);
                     break;
diff --git a/include/hw/loader.h b/include/hw/loader.h
index 5ed3fd8..e98b84b 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -226,7 +226,7 @@ void rom_set_fw(FWCfgState *f);
 void rom_set_order_override(int order);
 void rom_reset_order_override(void);
 int rom_copy(uint8_t *dest, hwaddr addr, size_t size);
-void *rom_ptr(hwaddr addr);
+void *rom_ptr(hwaddr addr, size_t size);
 void hmp_info_roms(Monitor *mon, const QDict *qdict);
 
 #define rom_add_file_fixed(_f, _a, _i)          \
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 9d030e0..6773f40 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -219,7 +219,7 @@ static void arm_cpu_reset(CPUState *s)
 
         /* Load the initial SP and PC from offset 0 and 4 in the vector table */
         vecbase = env->v7m.vecbase[env->v7m.secure];
-        rom = rom_ptr(vecbase);
+        rom = rom_ptr(vecbase, 8);
         if (rom) {
             /* Address zero is covered by ROM which hasn't yet been
              * copied into physical memory.
-- 
1.8.3.1