On 03/15/18 08:54, Kevin Wolf wrote:
Am 15.03.2018 um 06:19 hat Jack Schwartz geschrieben:
Hi Kevin.
My comments are inline...
On 2018-03-14 10:32, Kevin Wolf wrote:
The code path with a manually set mh_load_addr in the Multiboot header
checks that load_end_addr <= load_addr, but the path where load_end_addr
is automatically detected if 0 is given in the header misses the
corresponding check.
1) The code checks that load_end_addr >= load_addr (before letting it
through).
2) load_end_addr is used only when it is read in as non-zero, so no check is
needed if zero. (It gets debug-printed even when zero, but is used only to
calculate mb_load_size and only when non-zero.)
Oops, good point. I'll change the start of the commit message as follows:
The code path with a manually set mh_load_end_addr in the Multiboot
header checks that mh_load_end_addr >= mh_load_addr, but the path where
mh_load_end_addr is 0 in the header and therefore automatically
calculated from the file size misses the corresponding check.
Does this look better?
mb_load_size is calculated from the file size, not mh_load_end_addr, so
I think you mean mb_load_size rather than mh_load_end_addr. Do you
intend to say:
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 ischecked. However, mb_load_size is not checked when
calculated from thefile size, when mh_load_end_addr is 0.
Also, if this is what you intend to say, would the following code change
be more ofwhat you want:
Remove this:
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) {
and instead do this a few lines further down:
mb_kernel_size = mh_bss_end_addr - mh_load_addr;
} else {
mb_kernel_size = mb_load_size;
}
+ if (mb_kernel_size > UINT32_MAX - mh_load_addr) {
+ error_report("kernel does not fit in address space");
+ exit(1);
+ }
mb_debug("multiboot: header_addr = %#x", mh_header_addr);
mb_debug("multiboot: load_addr = %#x", mh_load_addr);
The reason would be to include the bss area in the calculation, when
mh_bss_end_addr is non-zero.
Thanks,
Jack
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.
Code itself looks fine.
Modulo above comments:
Reviewed-by: Jack Schwartz <jack.schwa...@oracle.com>
Thanks for your review of the series!
Kevin
