[PATCH] nfsd: nfsd should drop CAP_MKNOD for non-root

From: J. Bruce Fields
Date: Wed Mar 18 2009 - 12:21:52 EST


From: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>

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@xxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
---
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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