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[romprefix] Use correct size for PMM allocation of image source block

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iPXE allocates its first PMM block using the image source length,
which is rounded up to the nearest 16-byte paragraph.  It then copies
in data of a length calculated from the ROM size, which is
theoretically less than or equal to the image source length, but is
rounded up to the nearest 512-byte sector.  This can result in copying
beyond the end of the allocated PMM block, which can corrupt the PMM
data structures (and other essentially arbitrary areas of memory).

Fix by rounding up the image source length to the nearest 512-byte
sector before using it as the PMM allocation length.

Reported-by: Alex Williamson <alex.williamson@redhat.com>
Reported-by: Jarrod Johnson <jarrod.b.johnson@gmail.com>
Reported-by: Itay Gazit <itayg@mellanox.co.il>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown 2011-03-15 01:52:58 +00:00
parent c315ae0394
commit 23daab14a6
1 changed files with 7 additions and 6 deletions
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13
src/arch/i386/prefix/romprefix.S
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@ -320,7 +320,8 @@ pmm_scan:
/* We have PMM and so a 1kB stack: preserve whole registers */
pushal
/* Allocate image source PMM block */
movzwl image_source_len_pgh, %ecx
movzwl image_source_size, %ecx
shll $5, %ecx
movl $PMM_HANDLE_BASE_IMAGE_SOURCE, %ebx
movw $get_pmm_image_source, %bp
call get_pmm
@ -565,16 +566,16 @@ image_source:
.long 0
.size image_source, . - image_source
/* Image source area length (in paragraphs)
/* Image source size (in 512-byte sectors)
*
*/
image_source_len_pgh:
image_source_size:
.word 0
.size image_source_len_pgh, . - image_source_len_pgh
.size image_source_size, . - image_source_size
.section ".zinfo.fixup", "a", @progbits /* Compressor fixups */
.ascii "ADDW"
.long image_source_len_pgh
.long 16
.long image_source_size
.long 512
.long 0
.previous