In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
exfat: fix potential use-after-free in exfat_find_dir_entry()<\/p>\n
In exfat_find_dir_entry(), the buffer_head obtained from
\nexfat_get_dentry() is released with brelse(bh) before the fall-through
\nTYPE_EXTEND branch reads the directory entry through ep (which points
\ninto bh->b_data):<\/p>\n
\tbrelse(bh);
\n\tif (entry_type == TYPE_EXTEND) {
\n\t\t…
\n\t\tlen = exfat_extract_uni_name(ep, entry_uniname);
\n\t\t…
\n\t}<\/p>\n
After brelse() drops our reference, nothing guarantees that the
\nunderlying page backing bh->b_data remains valid for the subsequent
\nexfat_extract_uni_name() read. This is the same pattern fixed in
\ncommit fc961522ddbd (“exfat: Fix potential use after free in
\nexfat_load_upcase_table()”).<\/p>\n
Move brelse(bh) so it runs after ep is no longer dereferenced on
\neach branch.<\/p>\n
Confirmed on QEMU x86_64 with CONFIG_KASAN=y + CONFIG_DEBUG_PAGEALLOC=y
\n+ CONFIG_PAGE_POISONING=y on linux-next, using a crafted exFAT image
\n(long filename with same-hash collisions forcing the TYPE_EXTEND path).
\nWith a debug-only invalidate_bdev() inserted between brelse(bh) and
\nthe ep read to make the stale-deref window deterministic, the
\nunpatched kernel faults:<\/p>\n
BUG: KASAN: use-after-free in exfat_find_dir_entry+0x133b\/0x15a0
\n BUG: unable to handle page fault for address: ffff88801a5fa0c2
\n Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI
\n RIP: 0010:exfat_find_dir_entry+0x1188\/0x15a0<\/p>\n
With this patch applied, the same instrumented harness completes
\ncleanly under the same sanitizer stack. I have not reproduced a
\ncrash on an uninstrumented kernel under ordinary reclaim; the
\ninstrumented A\/B establishes the lifetime violation and that the
\npatch closes it, not an unaided triggerability claim.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
exfat: fix potential use-after-free in exfat_find_dir_entry()<\/p>\n
In exfat_find_dir_entry(), the buffer_head obtained from
\nexfat_get_d<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-14885","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/14885","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=14885"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14885"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14885"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}