[patch 36/88] add some long-missing capabilities to fs_mask

Greg KH
2009-04-30T17:23:27Z

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2.6.28-stable review patch. If anyone has any objections, please let us know.

------------------

From: Serge E. Hallyn <serue@us.ibm.com>

upstream commit: 0ad30b8fd5fe798aae80df6344b415d8309342cc

When POSIX capabilities were introduced during the 2.1 Linux
cycle, the fs mask, which represents the capabilities which having
fsuid==0 is supposed to grant, did not include CAP_MKNOD and
CAP_LINUX_IMMUTABLE. However, before capabilities the privilege
to call these did in fact depend upon fsuid==0.

This patch introduces those capabilities into the fsmask,
restoring the old behavior.

See the thread starting at http://lkml.org/lkml/2009/3/11/157 for
reference.

Note that if this fix is deemed valid, then earlier kernel versions (2.4
and 2.2) ought to be fixed too.

Changelog:
[Mar 23] Actually delete old CAP_FS_SET definition...
[Mar 20] Updated against J. Bruce Fields's patch

Reported-by: Igor Zhbanov <izh1979@gmail.com>
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: stable@kernel.org
Cc: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
include/linux/capability.h | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -366,7 +366,21 @@ typedef struct kernel_cap_struct {
#define CAP_FOR_EACH_U32(__capi) \
for (__capi = 0; __capi < _KERNEL_CAPABILITY_U32S; ++__capi)

+/*
+ * CAP_FS_MASK and CAP_NFSD_MASKS:
+ *
+ * The fs mask is all the privileges that fsuid==0 historically meant.
+ * At one time in the past, that included CAP_MKNOD and CAP_LINUX_IMMUTABLE.
+ *
+ * It has never meant setting security.* and trusted.* xattrs.
+ *
+ * We could also define fsmask as follows:
+ * 1. CAP_FS_MASK is the privilege to bypass all fs-related DAC permissions
+ * 2. The security.* and trusted.* xattrs are fs-related MAC permissions
+ */
+
# define CAP_FS_MASK_B0 (CAP_TO_MASK(CAP_CHOWN) \
+ | CAP_TO_MASK(CAP_MKNOD) \
| CAP_TO_MASK(CAP_DAC_OVERRIDE) \
| CAP_TO_MASK(CAP_DAC_READ_SEARCH) \
| CAP_TO_MASK(CAP_FOWNER) \
@@ -381,11 +395,12 @@ typedef struct kernel_cap_struct {
# define CAP_EMPTY_SET ((kernel_cap_t){{ 0, 0 }})
# 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_FS_SET ((kernel_cap_t){{ CAP_FS_MASK_B0 \
+ | CAP_TO_MASK(CAP_LINUX_IMMUTABLE), \
+ 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 } })
+ | CAP_TO_MASK(CAP_SYS_RESOURCE), \
+ CAP_FS_MASK_B1 } })

#endif /* _KERNEL_CAPABILITY_U32S != 2 */