linux-kernel - [PATCH] mm/mremap: fix regression in vrm->new

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250828032653.521314-1-cmllamas@google.com>
Date: Thu, 28 Aug 2025 03:26:52 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>
Cc: kernel-team@...roid.com, linux-kernel@...r.kernel.org, 
	Carlos Llamas <cmllamas@...gle.com>, "open list:MEMORY MAPPING" <linux-mm@...ck.org>
Subject: [PATCH] mm/mremap: fix regression in vrm->new_addr check

Commit 3215eaceca87 ("mm/mremap: refactor initial parameter sanity
checks") moved the sanity check for vrm->new_addr from mremap_to() to
check_mremap_params().

However, this caused a regression as vrm->new_addr is now checked even
when MREMAP_FIXED and MREMAP_DONTUNMAP flags are not specified. In this
case, vrm->new_addr can be garbage and create unexpected failures.

Fix this by moving the new_addr check after the vrm_implies_new_addr()
guard. This ensures that the new_addr is only checked when the user has
specified one explicitly.

Fixes: 3215eaceca87 ("mm/mremap: refactor initial parameter sanity checks")
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 mm/mremap.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index e618a706aff5..692acb0f9ea2 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -1771,18 +1771,17 @@ static unsigned long check_mremap_params(struct vma_remap_struct *vrm)
 	 * for DOS-emu "duplicate shm area" thing. But
 	 * a zero new-len is nonsensical.
 	 */
-	if (!vrm->new_len)
-		return -EINVAL;
-
-	/* Is the new length or address silly? */
-	if (vrm->new_len > TASK_SIZE ||
-	    vrm->new_addr > TASK_SIZE - vrm->new_len)
+	if (!vrm->new_len || vrm->new_len > TASK_SIZE)
 		return -EINVAL;
 
 	/* Remainder of checks are for cases with specific new_addr. */
 	if (!vrm_implies_new_addr(vrm))
 		return 0;
 
+	/* Is the new address silly? */
+	if (vrm->new_addr > TASK_SIZE - vrm->new_len)
+		return -EINVAL;
+
 	/* The new address must be page-aligned. */
 	if (offset_in_page(vrm->new_addr))
 		return -EINVAL;
-- 
2.51.0.268.g9569e192d0-goog