multiboot: validate multiboot header address values
PATCH 1/1 multiboot: validate multiboot header address values
From: Prasad J Pandit <[email protected]>
While loading kernel via multiboot-v1 image, (flags & 0x00010000) indicates that multiboot header contains valid addresses to load the kernel image. These addresses are used to compute kernel size and kernel text offset in the OS image. Validate these address values to avoid an OOB access issue.
--- hw/i386/multiboot.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
hw/i386/multiboot.c +19 -0
@@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,uint32_t mh_header_addr =ldl_p (header+i+12 );uint32_t mh_load_end_addr =ldl_p (header+i+20 );uint32_t mh_bss_end_addr =ldl_p (header+i+24 ); + mh_load_addr =ldl_p (header+i+16 ); +if (mh_header_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_addr address\n" ); +exit (1 ); + } +uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);uint32_t mb_load_size =0 ; mh_entry_addr =ldl_p (header+i+28 );if (mh_load_end_addr) { +if (mh_bss_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_bss_end_addr address\n" ); +exit (1 ); + } mb_kernel_size = mh_bss_end_addr - mh_load_addr; + +if (mh_load_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_end_addr address\n" ); +exit (1 ); + } mb_load_size = mh_load_end_addr - mh_load_addr; }else { +if (kernel_file_size < mb_kernel_text_offset) { +fprintf (stderr,"invalid kernel_file_size\n" ); +exit (1 ); + } mb_kernel_size = kernel_file_size - mb_kernel_text_offset; mb_load_size = mb_kernel_size; }
Signature · 1 line
2.13.5
Quoted 11 lines · P J P
From: Prasad J Pandit <[email protected]>
While loading kernel via multiboot-v1 image, (flags &
0x00010000) indicates that multiboot header contains valid addresses to load the kernel image. These addresses are used to compute kernel size and kernel text offset in the OS image. Validate these address values to avoid an OOB access issue.Reported-by Thomas Garnier <[email protected]>Signed-off-by Prasad J Pandit <[email protected]>---
Looks good, tested.
Quoted 45 lines
hw/i386/multiboot.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)hw/i386/multiboot.c +19
-1@@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,uint32_t mh_header_addr =ldl_p (header+i+12 );uint32_t mh_load_end_addr =ldl_p (header+i+20 );uint32_t mh_bss_end_addr =ldl_p (header+i+24 ); + mh_load_addr =ldl_p (header+i+16 ); +if (mh_header_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_addr address\n" ); +exit (1 ); + } +uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);uint32_t mb_load_size =0 ; mh_entry_addr =ldl_p (header+i+28 );if (mh_load_end_addr) { +if (mh_bss_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_bss_end_addr address\n" ); +exit (1 ); + } mb_kernel_size = mh_bss_end_addr - mh_load_addr; + +if (mh_load_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_end_addr address\n" ); +exit (1 ); + } mb_load_size = mh_load_end_addr - mh_load_addr; }else { +if (kernel_file_size < mb_kernel_text_offset) { +fprintf (stderr,"invalid kernel_file_size\n" ); +exit (1 ); + } mb_kernel_size = kernel_file_size - mb_kernel_text_offset; mb_load_size = mb_kernel_size; } --2.13.5
Signature · 1 line
Thomas
Quoted 9 lines · Thomas Garnier
Quoted 8 lines · P J P
From: Prasad J Pandit <[email protected]>
While loading kernel via multiboot-v1 image, (flags &
0x00010000) indicates that multiboot header contains valid addresses to load the kernel image. These addresses are used to compute kernel size and kernel text offset in the OS image. Validate these address values to avoid an OOB access issue.
Quoted 7 lines
Quoted 3 lines
Reported-by Thomas Garnier <[email protected]>Signed-off-by Prasad J Pandit <[email protected]>---
Looks good, tested.
Tested-by Thomas Garnier <[email protected]>
Btw, can you open a CVE for that? (and reference it in the commit).
Quoted 51 lines
Quoted 44 lines
hw/i386/multiboot.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)hw/i386/multiboot.c +19
-1@@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg,uint32_t mh_header_addr =ldl_p (header+i+12 );uint32_t mh_load_end_addr =ldl_p (header+i+20 );uint32_t mh_bss_end_addr =ldl_p (header+i+24 ); + mh_load_addr =ldl_p (header+i+16 ); +if (mh_header_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_addr address\n" ); +exit (1 ); + } +uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);uint32_t mb_load_size =0 ; mh_entry_addr =ldl_p (header+i+28 );if (mh_load_end_addr) { +if (mh_bss_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_bss_end_addr address\n" ); +exit (1 ); + } mb_kernel_size = mh_bss_end_addr - mh_load_addr; + +if (mh_load_end_addr < mh_load_addr) { +fprintf (stderr,"invalid mh_load_end_addr address\n" ); +exit (1 ); + } mb_load_size = mh_load_end_addr - mh_load_addr; }else { +if (kernel_file_size < mb_kernel_text_offset) { +fprintf (stderr,"invalid kernel_file_size\n" ); +exit (1 ); + } mb_kernel_size = kernel_file_size - mb_kernel_text_offset; mb_load_size = mb_kernel_size; } --Quoted 2 lines
2.13.5
--
Thomas
Signature · 1 line
Thomas
+-- On Tue, 5 Sep 2017, Thomas Garnier wrote --+ | Btw, can you open a CVE for that? (and reference it in the commit).
Done; Sent revised patch v1.
Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F