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staging: lustre: simplify capability dropping.

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Lustre has a 'squash credentials' concept similar to the "anon_uid"
for nfsd.  When accessing a file with squashed credentials, we
need to also drop capabilities.
Linux has cap_drop_fs_set() and cap_drop_nfsd_set().  Rather than
taking a completely different approach, this patch changes lustre
to use this same cap_drop_*_set() approach.

With this change we also drop CAP_MKNOD and CAP_MAC_OVERRIDE
which are probably appropriate, and don't drop
CAP_SYS_ADMIN or CAP_SYS_BOOT which should be irrelevant for
file permission checking

Calling both cap_drop_*_set() seems a bit clumsy, but gets
the job done.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
NeilBrown 2018-05-21 14:35:12 +10:00 • committed by Greg Kroah-Hartman
commit f497115d4c
2 changed files with 3 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

10
drivers/staging/lustre/include/linux/libcfs/curproc.h
View file

@ -50,16 +50,6 @@
typedef u32 cfs_cap_t;
#define CFS_CAP_FS_MASK (BIT(CAP_CHOWN) | \
BIT(CAP_DAC_OVERRIDE) | \
BIT(CAP_DAC_READ_SEARCH) | \
BIT(CAP_FOWNER) | \
BIT(CAP_FSETID) | \
BIT(CAP_LINUX_IMMUTABLE) | \
BIT(CAP_SYS_ADMIN) | \
BIT(CAP_SYS_BOOT) | \
BIT(CAP_SYS_RESOURCE))
static inline cfs_cap_t cfs_curproc_cap_pack(void)
{
/* cfs_cap_t is only the first word of kernel_cap_t */

8
drivers/staging/lustre/lustre/llite/file.c
View file

@ -3050,7 +3050,6 @@ int ll_inode_permission(struct inode *inode, int mask)
const struct cred *old_cred = NULL;
struct cred *cred = NULL;
bool squash_id = false;
cfs_cap_t cap;
int rc = 0;
if (mask & MAY_NOT_BLOCK)
@ -3094,10 +3093,9 @@ int ll_inode_permission(struct inode *inode, int mask)
cred->fsuid = make_kuid(&init_user_ns, squash->rsi_uid);
cred->fsgid = make_kgid(&init_user_ns, squash->rsi_gid);
for (cap = 0; cap < sizeof(cfs_cap_t) * 8; cap++) {
if ((1 << cap) & CFS_CAP_FS_MASK)
cap_lower(cred->cap_effective, cap);
}
cred->cap_effective = cap_drop_nfsd_set(cred->cap_effective);
cred->cap_effective = cap_drop_fs_set(cred->cap_effective);
old_cred = override_creds(cred);
}