On Tue, Apr 10, 2018 at 09:42:50AM -0500, Eric W. Biederman wrote:

Tetsuo Handa [off-list ref] writes:

quoted

From 904d07a6eb014f3df0c5a1ebfcfd4323276a9a76 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 10 Apr 2018 15:15:16 +0900
Subject: [PATCH] commoncap: Handle memory allocation failure.

syzbot is reporting NULL pointer dereference at xattr_getsecurity() [1],
for cap_inode_getsecurity() is returning sizeof(struct vfs_cap_data) when
memory allocation failed. Return -ENOMEM if memory allocation failed.

[1] https://syzkaller.appspot.com/bug?id=a55ba438506fe68649a5f50d2d82d56b365e0107

Acked-by: "Eric W. Biederman" <redacted>

Tetsuo I can pick this up, or do you have preferred path for getting
this change merged?

Serge does this fix look ok to you?  I am a bit worried that

yup, looks good to me.  would have replied an hour or two ago but lacked
an lkml-acceptable mailer :)

thanks,
serge

might be a bit brittler but I don't see any issues with this change.

Eric

quoted

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 8db6c34f1dbc8e06 ("Introduce v3 namespaced file capabilities")
Reported-by: syzbot <redacted>
Cc: stable <redacted> # 4.14+
Cc: Serge E. Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <redacted>
---
 security/commoncap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/commoncap.c b/security/commoncap.c
index 48620c9..1ce701f 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c

@@ -449,6 +449,8 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
 				magic |= VFS_CAP_FLAGS_EFFECTIVE;
 			memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
 			cap->magic_etc = cpu_to_le32(magic);
+		} else {
+			size = -ENOMEM;
 		}
 	}
 	kfree(tmpbuf);
--

1.8.3.1

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