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Message-Id: <20251008061027.work.515-kees@kernel.org>
Date: Tue, 7 Oct 2025 23:10:32 -0700
From: Kees Cook <kees@...nel.org>
To: Christian Brauner <brauner@...nel.org>
Cc: Kees Cook <kees@...nel.org>,
syzbot+a9391462075ffb9f77c6@...kaller.appspotmail.com,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
linux-media@...r.kernel.org,
dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org,
linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: [PATCH] dma-buf: use SB_I_NOEXEC and SB_I_NODEV
The dma-buf pseudo-filesystem should never have executable mappings nor
device nodes. Set SB_I_NOEXEC and SB_I_NODEV on the superblock to enforce
this at the filesystem level, similar to secretmem, commit 98f99394a104
("secretmem: use SB_I_NOEXEC").
Fix the syzbot-reported warning from the exec code to enforce this
requirement:
> WARNING: CPU: 1 PID: 6000 at fs/exec.c:119 path_noexec+0x1af/0x200 fs/exec.c:118
> Modules linked in:
> CPU: 1 UID: 0 PID: 6000 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> RIP: 0010:path_noexec+0x1af/0x200 fs/exec.c:118
> Call Trace:
> <TASK>
> do_mmap+0xa43/0x10d0 mm/mmap.c:469
> vm_mmap_pgoff+0x2a6/0x4d0 mm/util.c:580
> ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:604
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
Reported-by: syzbot+a9391462075ffb9f77c6@...kaller.appspotmail.com
Closes: https://lore.kernel.org/all/68dc3ade.a70a0220.10c4b.015b.GAE@google.com/
Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Christian Brauner <brauner@...nel.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Cc: "Christian König" <christian.koenig@....com>
Cc: syzbot+a9391462075ffb9f77c6@...kaller.appspotmail.com
Cc: <linux-media@...r.kernel.org>
Cc: <dri-devel@...ts.freedesktop.org>
Cc: <linaro-mm-sig@...ts.linaro.org>
---
drivers/dma-buf/dma-buf.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 2bcf9ceca997..6e2ab1a4560d 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -189,6 +189,8 @@ static int dma_buf_fs_init_context(struct fs_context *fc)
{
struct pseudo_fs_context *ctx;
+ fc->s_iflags |= SB_I_NOEXEC;
+ fc->s_iflags |= SB_I_NODEV;
ctx = init_pseudo(fc, DMA_BUF_MAGIC);
if (!ctx)
return -ENOMEM;
--
2.34.1
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