linux-kernel - [PATCH] nfsd: nfsd should drop CAP

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Date:	Wed, 18 Mar 2009 12:21:32 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Igor Zhbanov <izh1979@...il.com>,
	Serge Hallyn <serue@...ibm.com>,
	"J. Bruce Fields" <bfields@...i.umich.edu>, stable@...nel.org
Subject: [PATCH] nfsd: nfsd should drop CAP_MKNOD for non-root

From: J. Bruce Fields <bfields@...i.umich.edu>

Since creating a device node is normally an operation requiring special
privilege, Igor Zhbanov points out that it is surprising (to say the
least) that a client can, for example, create a device node on a
filesystem exported with root_squash.

So, make sure CAP_MKNOD is among the capabilities dropped when an nfsd
thread handles a request from a non-root user.

Reported-by: Igor Zhbanov <izh1979@...il.com>
Cc: stable@...nel.org
Signed-off-by: J. Bruce Fields <bfields@...i.umich.edu>
---
 include/linux/capability.h |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 1b98725..4864a43 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -393,8 +393,10 @@ struct cpu_vfs_cap_data {
 # define CAP_FULL_SET     ((kernel_cap_t){{ ~0, ~0 }})
 # define CAP_INIT_EFF_SET ((kernel_cap_t){{ ~CAP_TO_MASK(CAP_SETPCAP), ~0 }})
 # define CAP_FS_SET       ((kernel_cap_t){{ CAP_FS_MASK_B0, CAP_FS_MASK_B1 } })
-# define CAP_NFSD_SET     ((kernel_cap_t){{ CAP_FS_MASK_B0|CAP_TO_MASK(CAP_SYS_RESOURCE), \
-					CAP_FS_MASK_B1 } })
+# define CAP_NFSD_SET     ((kernel_cap_t){{ CAP_FS_MASK_B0 \
+					    | CAP_TO_MASK(CAP_SYS_RESOURCE) \
+					    | CAP_TO_MASK(CAP_MKNOD), \
+					    CAP_FS_MASK_B1 } })
 
 #endif /* _KERNEL_CAPABILITY_U32S != 2 */
 
-- 
1.6.0.4

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