linux-ext4 - [PATCH 2/7] e2fsck: fix potential out-of-bounds read in inc_ea_inode

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Date:   Tue,  7 Jun 2022 00:24:39 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     Nils Bars <nils.bars@....de>,
        Moritz Schlögel <moritz.schloegel@....de>,
        Nico Schiller <nico.schiller@....de>,
        "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 2/7] e2fsck: fix potential out-of-bounds read in inc_ea_inode_refs()

If there isn't enough space for a full extended attribute entry,
inc_ea_inode_refs() might end up reading beyond the allocated memory
buffer.

Reported-by: Nils Bars <nils.bars@....de>
Reported-by: Moritz Schlögel <moritz.schloegel@....de>
Reported-by: Nico Schiller <nico.schiller@....de>
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 e2fsck/pass1.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index dde862a8..2a17bb8a 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -389,13 +389,13 @@ static problem_t check_large_ea_inode(e2fsck_t ctx,
 static void inc_ea_inode_refs(e2fsck_t ctx, struct problem_context *pctx,
 			      struct ext2_ext_attr_entry *first, void *end)
 {
-	struct ext2_ext_attr_entry *entry;
+	struct ext2_ext_attr_entry *entry = first;
+	struct ext2_ext_attr_entry *np = EXT2_EXT_ATTR_NEXT(entry);
 
-	for (entry = first;
-	     (void *)entry < end && !EXT2_EXT_IS_LAST_ENTRY(entry);
-	     entry = EXT2_EXT_ATTR_NEXT(entry)) {
+	while ((void *) entry < end && (void *) np < end &&
+	       !EXT2_EXT_IS_LAST_ENTRY(entry)) {
 		if (!entry->e_value_inum)
-			continue;
+			goto next;
 		if (!ctx->ea_inode_refs) {
 			pctx->errcode = ea_refcount_create(0,
 							   &ctx->ea_inode_refs);
@@ -408,6 +408,9 @@ static void inc_ea_inode_refs(e2fsck_t ctx, struct problem_context *pctx,
 		}
 		ea_refcount_increment(ctx->ea_inode_refs, entry->e_value_inum,
 				      0);
+	next:
+		entry = np;
+		np = EXT2_EXT_ATTR_NEXT(entry);
 	}
 }
 
-- 
2.31.0