diff options
Diffstat (limited to 'system/xen/patches/xsa179-qemuu-4.6-0001-vga-fix-banked-access-bounds-checking-CVE-2016-3710.patch')
| -rw-r--r-- | system/xen/patches/xsa179-qemuu-4.6-0001-vga-fix-banked-access-bounds-checking-CVE-2016-3710.patch | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/system/xen/patches/xsa179-qemuu-4.6-0001-vga-fix-banked-access-bounds-checking-CVE-2016-3710.patch b/system/xen/patches/xsa179-qemuu-4.6-0001-vga-fix-banked-access-bounds-checking-CVE-2016-3710.patch new file mode 100644 index 0000000000..3ad3cf4327 --- /dev/null +++ b/system/xen/patches/xsa179-qemuu-4.6-0001-vga-fix-banked-access-bounds-checking-CVE-2016-3710.patch @@ -0,0 +1,108 @@ +From b16db5ab2d0c5ff755e08942f4c8e8f9f8618eae Mon Sep 17 00:00:00 2001 +From: Gerd Hoffmann <kraxel@redhat.com> +Date: Tue, 26 Apr 2016 08:49:10 +0200 +Subject: [PATCH 1/5] vga: fix banked access bounds checking (CVE-2016-3710) + +vga allows banked access to video memory using the window at 0xa00000 +and it supports a different access modes with different address +calculations. + +The VBE bochs extentions support banked access too, using the +VBE_DISPI_INDEX_BANK register. The code tries to take the different +address calculations into account and applies different limits to +VBE_DISPI_INDEX_BANK depending on the current access mode. + +Which is probably effective in stopping misprogramming by accident. +But from a security point of view completely useless as an attacker +can easily change access modes after setting the bank register. + +Drop the bogus check, add range checks to vga_mem_{readb,writeb} +instead. + +Fixes: CVE-2016-3710 +Reported-by: Qinghao Tang <luodalongde@gmail.com> +Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> +Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> +--- + hw/display/vga.c | 24 ++++++++++++++++++------ + 1 file changed, 18 insertions(+), 6 deletions(-) + +diff --git a/hw/display/vga.c b/hw/display/vga.c +index 52eaf05..b577712 100644 +--- a/hw/display/vga.c ++++ b/hw/display/vga.c +@@ -178,6 +178,7 @@ static void vga_update_memory_access(VGACommonState *s) + break; + } + base += isa_mem_base; ++ assert(offset + size <= s->vram_size); + memory_region_init_alias(&s->chain4_alias, memory_region_owner(&s->vram), + "vga.chain4", &s->vram, offset, size); + memory_region_add_subregion_overlap(s->legacy_address_space, base, +@@ -715,11 +716,7 @@ void vbe_ioport_write_data(void *opaque, uint32_t addr, uint32_t val) + vbe_fixup_regs(s); + break; + case VBE_DISPI_INDEX_BANK: +- if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) { +- val &= (s->vbe_bank_mask >> 2); +- } else { +- val &= s->vbe_bank_mask; +- } ++ val &= s->vbe_bank_mask; + s->vbe_regs[s->vbe_index] = val; + s->bank_offset = (val << 16); + vga_update_memory_access(s); +@@ -818,13 +815,21 @@ uint32_t vga_mem_readb(VGACommonState *s, hwaddr addr) + + if (s->sr[VGA_SEQ_MEMORY_MODE] & VGA_SR04_CHN_4M) { + /* chain 4 mode : simplest access */ ++ assert(addr < s->vram_size); + ret = s->vram_ptr[addr]; + } else if (s->gr[VGA_GFX_MODE] & 0x10) { + /* odd/even mode (aka text mode mapping) */ + plane = (s->gr[VGA_GFX_PLANE_READ] & 2) | (addr & 1); +- ret = s->vram_ptr[((addr & ~1) << 1) | plane]; ++ addr = ((addr & ~1) << 1) | plane; ++ if (addr >= s->vram_size) { ++ return 0xff; ++ } ++ ret = s->vram_ptr[addr]; + } else { + /* standard VGA latched access */ ++ if (addr * sizeof(uint32_t) >= s->vram_size) { ++ return 0xff; ++ } + s->latch = ((uint32_t *)s->vram_ptr)[addr]; + + if (!(s->gr[VGA_GFX_MODE] & 0x08)) { +@@ -881,6 +886,7 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val) + plane = addr & 3; + mask = (1 << plane); + if (s->sr[VGA_SEQ_PLANE_WRITE] & mask) { ++ assert(addr < s->vram_size); + s->vram_ptr[addr] = val; + #ifdef DEBUG_VGA_MEM + printf("vga: chain4: [0x" TARGET_FMT_plx "]\n", addr); +@@ -894,6 +900,9 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val) + mask = (1 << plane); + if (s->sr[VGA_SEQ_PLANE_WRITE] & mask) { + addr = ((addr & ~1) << 1) | plane; ++ if (addr >= s->vram_size) { ++ return; ++ } + s->vram_ptr[addr] = val; + #ifdef DEBUG_VGA_MEM + printf("vga: odd/even: [0x" TARGET_FMT_plx "]\n", addr); +@@ -967,6 +976,9 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val) + mask = s->sr[VGA_SEQ_PLANE_WRITE]; + s->plane_updated |= mask; /* only used to detect font change */ + write_mask = mask16[mask]; ++ if (addr * sizeof(uint32_t) >= s->vram_size) { ++ return; ++ } + ((uint32_t *)s->vram_ptr)[addr] = + (((uint32_t *)s->vram_ptr)[addr] & ~write_mask) | + (val & write_mask); +-- +1.9.1 + |