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multiboot: Reject kernels exceeding the address space

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The code path where mh_load_end_addr is non-zero in the Multiboot
header checks that mh_load_end_addr >= mh_load_addr and so
mb_load_size is checked.  However, mb_load_size is not checked when
calculated from the file size, when mh_load_end_addr is 0.

If the kernel binary size is larger than can fit in the address space
after load_addr, we ended up with a kernel_size that is smaller than
load_size, which means that we read the file into a too small buffer.

Add a check to reject kernel files with such Multiboot headers.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
This commit is contained in:
Kevin Wolf 2018-03-14 17:46:38 +01:00
parent f1a63fcfcd
commit b17a9054a0
1 changed files with 4 additions and 0 deletions
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4
hw/i386/multiboot.c
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@ -247,6 +247,10 @@ int load_multiboot(FWCfgState *fw_cfg,
}
mb_load_size = kernel_file_size - mb_kernel_text_offset;
}
if (mb_load_size > UINT32_MAX - mh_load_addr) {
error_report("kernel does not fit in address space");
exit(1);
}
if (mh_bss_end_addr) {
if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
error_report("invalid bss_end_addr address");