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multiboot: validate multiboot header address values

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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.

This is CVE-2017-14167.

Reported-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Message-Id: <20170907063256.7418-1-ppandit@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Prasad J Pandit 2017-09-07 12:02:56 +05:30 committed by Paolo Bonzini
parent 80cac47e95
commit ed4f86e8b6
1 changed files with 19 additions and 0 deletions
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19
hw/i386/multiboot.c
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@ -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;
}