+ ocfs2-abstract-the-fast-symlink-nul-termination-check.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ocfs2: abstract the fast symlink NUL-termination check
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-abstract-the-fast-symlink-nul-termination-check.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-abstract-the-fast-symlink-nul-termination-check.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Joseph Qi <joseph.qi@linux.alibaba.com>
Subject: ocfs2: abstract the fast symlink NUL-termination check
Date: Mon, 09 Nov 2026 20:21:04 +0800

Fold the strnlen() test into a predicate that bounds the read itself
against ocfs2_fast_symlink_chars(), which is exactly the space available
for id2.i_symlink in the inode block.

The open-coded version was only safe because the preceding i_size check
had already bailed: i_size comes from disk, so an unbounded strnlen() on
i_size + 1 bytes can run past the end of the buffer.  Keeping that
ordering dependency implicit in a helper would be fragile, especially
once the filecheck variant starts calling it, so the predicate returns
false for an oversized i_size and leaves that case to
ocfs2_dinode_has_oversized_fast_symlink().

At the existing call site the size check still runs first, so behaviour
is unchanged.

No functional change intended.

Link: https://lore.kernel.org/20261109122121.21473-15-joseph.qi@linux.alibaba.com
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
---

 fs/ocfs2/inode.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

--- a/fs/ocfs2/inode.c~ocfs2-abstract-the-fast-symlink-nul-termination-check
+++ a/fs/ocfs2/inode.c
@@ -207,6 +207,25 @@ static bool ocfs2_dinode_has_oversized_f
 	return le64_to_cpu(di->i_size) >= ocfs2_fast_symlink_chars(sb);
 }
 
+static bool ocfs2_dinode_has_unterminated_fast_symlink(struct super_block *sb,
+						       struct ocfs2_dinode *di)
+{
+	u64 i_size = le64_to_cpu(di->i_size);
+
+	/*
+	 * Bound the strnlen() here rather than relying on the caller having
+	 * rejected an oversized i_size first.  i_size comes from disk, and
+	 * ocfs2_fast_symlink_chars() is exactly the space available in the
+	 * inode block, so without this bound the read can run past it.
+	 * An oversized i_size is reported by
+	 * ocfs2_dinode_has_oversized_fast_symlink() instead.
+	 */
+	if (i_size >= ocfs2_fast_symlink_chars(sb))
+		return false;
+
+	return strnlen((char *)di->id2.i_symlink, i_size + 1) != i_size;
+}
+
 void ocfs2_set_inode_flags(struct inode *inode)
 {
 	unsigned int flags = OCFS2_I(inode)->ip_attr;
@@ -1812,7 +1831,7 @@ int ocfs2_validate_inode_block(struct su
 			goto bail;
 		}
 
-		if (strnlen((char *)di->id2.i_symlink, i_size + 1) != i_size) {
+		if (ocfs2_dinode_has_unterminated_fast_symlink(sb, di)) {
 			rc = ocfs2_error(sb,
 					 "Invalid dinode #%llu: fast symlink is not NUL-terminated at i_size %llu\n",
 					 (unsigned long long)bh->b_blocknr,
_

Patches currently in -mm which might be from joseph.qi@linux.alibaba.com are

ocfs2-exempt-orphaned-dinodes-from-the-zero-nlink-check.patch
ocfs2-abstract-the-zero-nlink-or-mode-dinode-check.patch
ocfs2-abstract-the-dinode-i_blkno-mismatch-check.patch
ocfs2-abstract-the-dinode-ocfs2_valid_fl-check.patch
ocfs2-abstract-the-dinode-fs_generation-mismatch-check.patch
ocfs2-abstract-the-dinode-suballoc-slot-checks.patch
ocfs2-abstract-the-dinode-suballoc-bit-check.patch
ocfs2-abstract-the-dinode-orphaned-slot-check.patch
ocfs2-abstract-the-dinode-dio-orphaned-slot-check.patch
ocfs2-abstract-the-inline-data-dinode-guard-and-cluster-check.patch
ocfs2-abstract-the-inline-data-id_count-bound-check.patch
ocfs2-abstract-the-inline-data-i_size-bound-check.patch
ocfs2-abstract-the-fast-symlink-dinode-guard-and-size-check.patch
ocfs2-abstract-the-fast-symlink-nul-termination-check.patch
ocfs2-abstract-the-chain-list-dinode-guard-and-count-check.patch
ocfs2-abstract-the-chain-list-next-free-record-check.patch
ocfs2-abstract-the-chain-list-bits-per-cluster-check.patch
ocfs2-abstract-the-dinode-refcount-location-check.patch
ocfs2-abstract-the-zero-extent-list-count-check.patch
ocfs2-abstract-the-oversized-extent-list-count-check.patch
ocfs2-abstract-the-extent-list-next-free-record-check.patch
ocfs2-report-unrepairable-corruption-from-online-filecheck-fix.patch
ocfs2-check-dinode-nlink-and-mode-in-online-filecheck.patch
ocfs2-check-dinode-suballoc-slot-in-online-filecheck.patch
ocfs2-check-dinode-suballoc-bit-in-online-filecheck.patch
ocfs2-check-dinode-orphaned-slots-in-online-filecheck.patch
ocfs2-check-inline-data-dinodes-in-online-filecheck.patch
ocfs2-check-fast-symlink-dinodes-in-online-filecheck.patch
ocfs2-check-chain-list-dinodes-in-online-filecheck.patch
ocfs2-check-dinode-refcount-location-in-online-filecheck.patch
ocfs2-check-extent-list-dinodes-in-online-filecheck.patch