Bug 2516353 (CVE-2026-72196) - CVE-2026-72196 kernel: fs/ntfs3: bound copy_lcns dp->page_lcns[] index in analysis pass
Summary: CVE-2026-72196 kernel: fs/ntfs3: bound copy_lcns dp->page_lcns[] index in ana...
Keywords:
Status: NEW
Alias: CVE-2026-72196
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-15 06:08 UTC by OSIDB Bzimport
Modified: 2026-08-18 15:05 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-08-15 06:08:04 UTC
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: bound copy_lcns dp->page_lcns[] index in analysis pass

In log_replay()'s analysis pass, after find_dp() returns a
valid DIR_PAGE_ENTRY for the (target_attr, target_vcn) tuple,
the copy_lcns block walks lrh->lcns_follow further entries:

	t16 = le16_to_cpu(lrh->lcns_follow);
	for (i = 0; i < t16; i++) {
	    size_t j = (size_t)(le64_to_cpu(lrh->target_vcn) -
	                        le64_to_cpu(dp->vcn));
	    dp->page_lcns[j + i] = lrh->page_lcns[i];
	}

find_dp() only validates that target_vcn falls within
[dp->vcn, dp->vcn + dp->lcns_follow), i.e., that the FIRST
cluster is covered.  The walk through the further entries is
not bounded against dp->lcns_follow.  For a malformed LRH
where target_vcn = dp->vcn + dp->lcns_follow - 1 and
lrh->lcns_follow > 1, the i > 0 writes overflow the dp's
allocated page_lcns[] array.

Add the missing j + lrh->lcns_follow <= dp->lcns_follow guard.

Reproduced under UML+KASAN on mainline 8d90b09e6741 as a
slab-out-of-bounds write of size 8 from log_replay+0x68d4 on
the mount path.

This is distinct from Pavitra Jha's 2026-05-02 patch
("fs/ntfs3: validate lcns_follow in log_replay conversion",
<20260502154252.164586-1-jhapavitra98>) which
addresses the separate version-0 dirty-page-table conversion
path's memmove(&dp->vcn, ...) call.  The two fixes are
complementary; both should land.

[almaz.alexandrovich: clang-formatted the changes,
fixed conflicts]


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