In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
PCI\/sysfs: Fix out-of-bounds read in pci_write_legacy_io()<\/p>\n
pci_write_legacy_io() loads 4 bytes from the kernfs write buffer
\nregardless of how many bytes userspace wrote:<\/p>\n
if (count != 1 && count != 2 && count != 4)
\n return -EINVAL;<\/p>\n
return pci_legacy_write(bus, off, *(u32 *)buf, count);<\/p>\n
kernfs_fop_write_iter() allocates the buffer with kmalloc(len + 1),
\nso a 1-byte write to the legacy_io sysfs file allocates 2 bytes and
\nthe unconditional u32 load reads up to 2 bytes past the end of the
\nallocation, which KASAN reports as a slab-out-of-bounds read.
\nSimilarly, a 2-byte write overreads by 1 byte.<\/p>\n
Thus, read only the number of bytes requested using get_unaligned_le16()
\nand get_unaligned_le32() for the 2 and 4 byte cases, interpreting the
\nbuffer as little-endian to match the byte ordering of PCI I\/O port
\nspace.<\/p>\n
The PowerPC implementation previously compensated for the generic
\ncode’s native-endian 32-bit load by shifting the value into place
\nfor the 1 and 2 byte cases. The shifts were only correct on
\nbig-endian kernels.<\/p>\n
On little-endian PowerPC (POWER8 and later), they extracted the wrong
\nbytes, so a 1-byte write wrote an out-of-bounds byte instead of the
\nrequested value. On big-endian, the native load also caused out_le16()
\nand out_le32() to reverse the user’s bytes on the wire for 2 and 4 byte
\nwrites. The little-endian helpers resolve both issues, so the shifts
\nare removed.<\/p>\n
No changes are needed for the Alpha platform.<\/p>\n
The legacy_io file is root-only and exists only on Alpha and PowerPC,
\nthe two architectures that define HAVE_PCI_LEGACY.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
PCI\/sysfs: Fix out-of-bounds read in pci_write_legacy_io()<\/p>\n
pci_write_legacy_io() loads 4 bytes from the kernfs write buffer
\nregard<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21644","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21644","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21644"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21644"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21644"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}