It isn't needed. If you don't set the type of the data associated with
that type it is a pretty obvious programming bug. So why waste the cycles?
Signed-off-by: Eric Paris <eparis@redhat.com>
We pay a rather large overhead initializing the common_audit_data.
Since we only need this information if we actually emit an audit
message there is little need to set it up in the hot path. This patch
splits the functionality of avc_has_perm() into avc_has_perm_noaudit(),
avc_audit_required() and slow_avc_audit(). But we take care of setting
up to audit between required() and the actual audit call. Thus saving
measurable time in a hot path.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Eric Paris <eparis@redhat.com>
It just bloats the audit data structure for no good reason, since the
only time those fields are filled are just before calling the
common_lsm_audit() function, which is also the only user of those
fields.
So just make them be the arguments to common_lsm_audit(), rather than
bloating that structure that is passed around everywhere, and is
initialized in hot paths.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Instead of declaring the entire selinux_audit_data on the stack when we
start an operation on declare it on the stack if we are going to use it.
We know it's usefulness at the end of the security decision and can declare
it there.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linus found that the gigantic size of the common audit data caused a big
perf hit on something as simple as running stat() in a loop. This patch
requires LSMs to declare the LSM specific portion separately rather than
doing it in a union. Thus each LSM can be responsible for shrinking their
portion and don't have to pay a penalty just because other LSMs have a
bigger space requirement.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that all the slow-path code is gone from these functions, we can
inline them into the main caller - avc_has_perm_flags().
Now the compiler can see that 'avc' is allocated on the stack for this
case, which helps register pressure a bit. It also actually shrinks the
total stack frame, because the stack frame that avc_has_perm_flags()
always needed (for that 'avc' allocation) is now sufficient for the
inlined functions too.
Inlining isn't bad - but mindless inlining of cold code (see the
previous commit) is.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The selinux AVC paths remain some of the hottest (and deepest) codepaths
at filename lookup time, and we make it worse by having the slow path
cases take up I$ and stack space even when they don't trigger. Gcc
tends to always want to inline functions that are just called once -
never mind that this might make for slower and worse code in the caller.
So this tries to improve on it a bit by making the slow-path cases
explicitly separate functions that are marked noinline, causing gcc to
at least no longer allocate stack space for them unless they are
actually called. It also seems to help register allocation a tiny bit,
since gcc now doesn't take the slow case code into account.
Uninlining the slow path may also allow us to inline the remaining hot
path into the one caller that actually matters: avc_has_perm_flags().
I'll have to look at that separately, but both avc_audit() and
avc_has_perm_noaudit() are now small and lean enough that inlining them
may make sense.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
avc_audit() did a lot of jumping around and had a big stack frame, all
for the uncommon case.
Split up the uncommon case (which we really can't make go fast anyway)
into its own slow function, and mark the conditional branches
appropriately for the common likely case.
This causes avc_audit() to no longer show up as one of the hottest
functions on the branch profiles (the new "perf -b" thing), and makes
the cycle profiles look really nice and dense too.
The whole audit path is still annoyingly very much one of the biggest
costs of name lookup, so these things are worth optimizing for. I wish
we could just tell people to turn it off, but realistically we do need
it: we just need to make sure that the overhead of the necessary evil is
as low as possible.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Right now security_get_user_sids() will pass in a NULL avd pointer to
avc_has_perm_noaudit(), which then forces that function to have a dummy
entry for that case and just generally test it.
Don't do it. The normal callers all pass a real avd pointer, and this
helper function is incredibly hot. So don't make avc_has_perm_noaudit()
do conditional stuff that isn't needed for the common case.
This also avoids some duplicated stack space.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is no point in counting hits - we can calculate it from the number
of lookups and misses.
This makes the avc statistics a bit smaller, and makes the code
generation better too.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
You can turn off the avc cache stats, but distributions seem to not do
that (perhaps because several performance tuning how-to's talk about the
avc cache statistics).
Which is sad, because the code it generates is truly horrendous, with
the statistics update being sandwitched between get_cpu/put_cpu which in
turn causes preemption disables etc. We're talking ten+ instructions
just to increment a per-cpu variable in some pretty hot code.
Fix the craziness by just using 'this_cpu_inc()' instead. Suddenly we
only need a single 'inc' instruction to increment the statistics. This
is quite noticeable in the incredibly hot avc_has_perm_noaudit()
function (which triggers all the statistics by virtue of doing an
avc_lookup() call).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that the security modules can decide whether they support the
dcache RCU walk or not it's possible to make selinux a bit more
RCU friendly. The SELinux AVC and security server access decision
code is RCU safe. A specific piece of the LSM audit code may not
be RCU safe.
This patch makes the VFS RCU walk retry if it would hit the non RCU
safe chunk of code. It will normally just work under RCU. This is
done simply by passing the VFS RCU state as a flag down into the
avc_audit() code and returning ECHILD there if it would have an issue.
Based-on-patch-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The lsm common audit code has wacky contortions making sure which pieces
of information are set based on if it was given a path, dentry, or
inode. Split this into path and inode to get rid of some of the code
complexity.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Now that the security modules can decide whether they support the
dcache RCU walk or not it's possible to make selinux a bit more
RCU friendly. The SELinux AVC and security server access decision
code is RCU safe. A specific piece of the LSM audit code may not
be RCU safe.
This patch makes the VFS RCU walk retry if it would hit the non RCU
safe chunk of code. It will normally just work under RCU. This is
done simply by passing the VFS RCU state as a flag down into the
avc_audit() code and returning ECHILD there if it would have an issue.
Based-on-patch-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Currently there are a number of applications (nautilus being the main one) which
calls access() on files in order to determine how they should be displayed. It
is normal and expected that nautilus will want to see if files are executable
or if they are really read/write-able. access() should return the real
permission. SELinux policy checks are done in access() and can result in lots
of AVC denials as policy denies RWX on files which DAC allows. Currently
SELinux must dontaudit actual attempts to read/write/execute a file in
order to silence these messages (and not flood the logs.) But dontaudit rules
like that can hide real attacks. This patch addes a new common file
permission audit_access. This permission is special in that it is meaningless
and should never show up in an allow rule. Instead the only place this
permission has meaning is in a dontaudit rule like so:
dontaudit nautilus_t sbin_t:file audit_access
With such a rule if nautilus just checks access() we will still get denied and
thus userspace will still get the correct answer but we will not log the denial.
If nautilus attempted to actually perform one of the forbidden actions
(rather than just querying access(2) about it) we would still log a denial.
This type of dontaudit rule should be used sparingly, as it could be a
method for an attacker to probe the system permissions without detection.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen D. Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Remove all rcu head inits. We don't care about the RCU head state before passing
it to call_rcu() anyway. Only leave the "on_stack" variants so debugobjects can
keep track of objects on stack.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: James Morris <jmorris@namei.org>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: James Morris <jmorris@namei.org>
Most of the LSM common audit work uses LSM_AUDIT_DATA_* for the naming.
This was not so for LSM_AUDIT_NO_AUDIT which means the generic initializer
cannot be used. This patch just renames the flag so the generic
initializer can be used.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
If allow_unknown==deny, SELinux treats an undefined kernel security
class as an error condition rather than as a typical permission denial
and thus does not allow permissions on undefined classes even when in
permissive mode. Change the SELinux logic so that this case is handled
as a typical permission denial, subject to the usual permissive mode and
permissive domain handling.
Also drop the 'requested' argument from security_compute_av() and
helpers as it is a legacy of the original security server interface and
is unused.
Changes:
- Handle permissive domains consistently by moving up the test for a
permissive domain.
- Make security_compute_av_user() consistent with security_compute_av();
the only difference now is that security_compute_av() performs mapping
between the kernel-private class and permission indices and the policy
values. In the userspace case, this mapping is handled by libselinux.
- Moved avd_init inside the policy lock.
Based in part on a patch by Paul Moore <paul.moore@hp.com>.
Reported-by: Andrew Worsley <amworsley@gmail.com>
Signed-off-by: Stephen D. Smalley <sds@tycho.nsa.gov>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
Historically we've seen cases where permissions are requested for classes
where they do not exist. In particular we have seen CIFS forget to set
i_mode to indicate it is a directory so when we later check something like
remove_name we have problems since it wasn't defined in tclass file. This
used to result in a avc which included the permission 0x2000 or something.
Currently the kernel will deny the operations (good thing) but will not
print ANY information (bad thing). First the auditdeny field is no
extended to include unknown permissions. After that is fixed the logic in
avc_dump_query to output this information isn't right since it will remove
the permission from the av and print the phrase "<NULL>". This takes us
back to the behavior before the classmap rewrite.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Modify SELinux to dynamically discover class and permission values
upon policy load, based on the dynamic object class/perm discovery
logic from libselinux. A mapping is created between kernel-private
class and permission indices used outside the security server and the
policy values used within the security server.
The mappings are only applied upon kernel-internal computations;
similar mappings for the private indices of userspace object managers
is handled on a per-object manager basis by the userspace AVC. The
interfaces for compute_av and transition_sid are split for kernel
vs. userspace; the userspace functions are distinguished by a _user
suffix.
The kernel-private class indices are no longer tied to the policy
values and thus do not need to skip indices for userspace classes;
thus the kernel class index values are compressed. The flask.h
definitions were regenerated by deleting the userspace classes from
refpolicy's definitions and then regenerating the headers. Going
forward, we can just maintain the flask.h, av_permissions.h, and
classmap.h definitions separately from policy as they are no longer
tied to the policy values. The next patch introduces a utility to
automate generation of flask.h and av_permissions.h from the
classmap.h definitions.
The older kernel class and permission string tables are removed and
replaced by a single security class mapping table that is walked at
policy load to generate the mapping. The old kernel class validation
logic is completely replaced by the mapping logic.
The handle unknown logic is reworked. reject_unknown=1 is handled
when the mappings are computed at policy load time, similar to the old
handling by the class validation logic. allow_unknown=1 is handled
when computing and mapping decisions - if the permission was not able
to be mapped (i.e. undefined, mapped to zero), then it is
automatically added to the allowed vector. If the class was not able
to be mapped (i.e. undefined, mapped to zero), then all permissions
are allowed for it if allow_unknown=1.
avc_audit leverages the new security class mapping table to lookup the
class and permission names from the kernel-private indices.
The mdp program is updated to use the new table when generating the
class definitions and allow rules for a minimal boot policy for the
kernel. It should be noted that this policy will not include any
userspace classes, nor will its policy index values for the kernel
classes correspond with the ones in refpolicy (they will instead match
the kernel-private indices).
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Before SELinux is disabled at boot it can create AVC entries. This patch
will flush those entries before disabling SELinux.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Move the avc_cache flushing into it's own function so it can be reused when
disabling SELinux.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Convert avc_audit in security/selinux/avc.c to use lsm_audit.h,
for better maintainability.
- changed selinux to use common_audit_data instead of
avc_audit_data
- eliminated code in avc.c and used code from lsm_audit.h instead.
Had to add a LSM_AUDIT_NO_AUDIT to lsm_audit.h so that avc_audit
can call common_lsm_audit and do the pre and post callbacks without
doing the actual dump. This makes it so that the patched version
behaves the same way as the unpatched version.
Also added a denied field to the selinux_audit_data private space,
once again to make it so that the patched version behaves like the
unpatched.
I've tested and confirmed that AVCs look the same before and after
this patch.
Signed-off-by: Thomas Liu <tliu@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Convert avc_audit in security/selinux/avc.c to use lsm_audit.h,
for better maintainability and for less code duplication.
- changed selinux to use common_audit_data instead of
avc_audit_data
- eliminated code in avc.c and used code from lsm_audit.h instead.
I have tested to make sure that the avcs look the same before and
after this patch.
Signed-off-by: Thomas Liu <tliu@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Added a call to free the avc_node_cache when inside selinux_disable because
it should not waste resources allocated during avc_init if SELinux is disabled
and the cache will never be used.
Signed-off-by: Thomas Liu <tliu@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
The attached patch adds support to generate audit messages on two cases.
The first one is a case when a multi-thread process tries to switch its
performing security context using setcon(3), but new security context is
not bounded by the old one.
type=SELINUX_ERR msg=audit(1245311998.599:17): \
op=security_bounded_transition result=denied \
oldcontext=system_u:system_r:httpd_t:s0 \
newcontext=system_u:system_r:guest_webapp_t:s0
The other one is a case when security_compute_av() masked any permissions
due to the type boundary violation.
type=SELINUX_ERR msg=audit(1245312836.035:32): \
op=security_compute_av reason=bounds \
scontext=system_u:object_r:user_webapp_t:s0 \
tcontext=system_u:object_r:shadow_t:s0:c0 \
tclass=file perms=getattr,open
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
This patch enables applications to handle permissive domain correctly.
Since the v2.6.26 kernel, SELinux has supported an idea of permissive
domain which allows certain processes to work as if permissive mode,
even if the global setting is enforcing mode.
However, we don't have an application program interface to inform
what domains are permissive one, and what domains are not.
It means applications focuses on SELinux (XACE/SELinux, SE-PostgreSQL
and so on) cannot handle permissive domain correctly.
This patch add the sixth field (flags) on the reply of the /selinux/access
interface which is used to make an access control decision from userspace.
If the first bit of the flags field is positive, it means the required
access control decision is on permissive domain, so application should
allow any required actions, as the kernel doing.
This patch also has a side benefit. The av_decision.flags is set at
context_struct_compute_av(). It enables to check required permissions
without read_lock(&policy_rwlock).
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Eric Paris <eparis@redhat.com>
--
security/selinux/avc.c | 2 +-
security/selinux/include/security.h | 4 +++-
security/selinux/selinuxfs.c | 4 ++--
security/selinux/ss/services.c | 30 +++++-------------------------
4 files changed, 11 insertions(+), 29 deletions(-)
Signed-off-by: James Morris <jmorris@namei.org>
We do not need O(1) access to the tail of the avc cache lists and so we are
wasting lots of space using struct list_head instead of struct hlist_head.
This patch converts the avc cache to use hlists in which there is a single
pointer from the head which saves us about 4k of global memory.
Resulted in about a 1.5% decrease in time spent in avc_has_perm_noaudit based
on oprofile sampling of tbench. Although likely within the noise....
Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
The code making use of struct avc_cache was not easy to read thanks to liberal
use of &avc_cache.{slots_lock,slots}[hvalue] throughout. This patch simply
creates local pointers and uses those instead of the long global names.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
It appears there was an intention to have the security server only decide
certain permissions and leave other for later as some sort of a portential
performance win. We are currently always deciding all 32 bits of
permissions and this is a useless couple of branches and wasted space.
This patch completely drops the av.decided concept.
This in a 17% reduction in the time spent in avc_has_perm_noaudit
based on oprofile sampling of a tbench benchmark.
Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
we are often needlessly jumping through hoops when it comes to avd
entries in avc_has_perm_noaudit and we have extra initialization and memcpy
which are just wasting performance. Try to clean the function up a bit.
This patch resulted in a 13% drop in time spent in avc_has_perm_noaudit in my
oprofile sampling of a tbench benchmark.
Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Currently SELinux code has an atomic which was intended to track how many
times an avc entry was used and to evict entries when they haven't been
used recently. Instead we never let this atomic get above 1 and evict when
it is first checked for eviction since it hits zero. This is a total waste
of time so I'm completely dropping ae.used.
This change resulted in about a 3% faster avc_has_perm_noaudit when running
oprofile against a tbench benchmark.
Signed-off-by: Eric Paris <eparis@redhat.com>
Reviewed by: Paul Moore <paul.moore@hp.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
The avc update node callbacks do not check the seqno of the caller with the
seqno of the node found. It is possible that a policy change could happen
(although almost impossibly unlikely) in which a permissive or
permissive_domain decision is not valid for the entry found. Simply pass
and check that the seqno of the caller and the seqno of the node found
match.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
I started playing with pahole today and decided to put it against the
selinux structures. Found we could save a little bit of space on x86_64
(and no harm on i686) just reorganizing some structs.
Object size changes:
av_inherit: 24 -> 16
selinux_class_perm: 48 -> 40
context: 80 -> 72
Admittedly there aren't many of av_inherit or selinux_class_perm's in
the kernel (33 and 1 respectively) But the change to the size of struct
context reverberate out a bit. I can get some hard number if they are
needed, but I don't see why they would be. We do change which cacheline
context->len and context->str would be on, but I don't see that as a
problem since we are clearly going to have to load both if the context
is to be of any value. I've run with the patch and don't seem to be
having any problems.
An example of what's going on using struct av_inherit would be:
form: to:
struct av_inherit { struct av_inherit {
u16 tclass; const char **common_pts;
const char **common_pts; u32 common_base;
u32 common_base; u16 tclass;
};
(notice all I did was move u16 tclass to the end of the struct instead
of the beginning)
Memory layout before the change:
struct av_inherit {
u16 tclass; /* 2 */
/* 6 bytes hole */
const char** common_pts; /* 8 */
u32 common_base; /* 4 */
/* 4 byes padding */
/* size: 24, cachelines: 1 */
/* sum members: 14, holes: 1, sum holes: 6 */
/* padding: 4 */
};
Memory layout after the change:
struct av_inherit {
const char ** common_pts; /* 8 */
u32 common_base; /* 4 */
u16 tclass; /* 2 */
/* 2 bytes padding */
/* size: 16, cachelines: 1 */
/* sum members: 14, holes: 0, sum holes: 0 */
/* padding: 2 */
};
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Using NIPQUAD() with NIPQUAD_FMT, %d.%d.%d.%d or %u.%u.%u.%u
can be replaced with %pI4
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The iscsi_ibft.c changes are almost certainly a bugfix as the
pointer 'ip' is a u8 *, so they never print the last 8 bytes
of the IPv6 address, and the eight bytes they do print have
a zero byte with them in each 16-bit word.
Other than that, this should cause no difference in functionality.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The purpose of this patch is to assign per-thread security context
under a constraint. It enables multi-threaded server application
to kick a request handler with its fair security context, and
helps some of userspace object managers to handle user's request.
When we assign a per-thread security context, it must not have wider
permissions than the original one. Because a multi-threaded process
shares a single local memory, an arbitary per-thread security context
also means another thread can easily refer violated information.
The constraint on a per-thread security context requires a new domain
has to be equal or weaker than its original one, when it tries to assign
a per-thread security context.
Bounds relationship between two types is a way to ensure a domain can
never have wider permission than its bounds. We can define it in two
explicit or implicit ways.
The first way is using new TYPEBOUNDS statement. It enables to define
a boundary of types explicitly. The other one expand the concept of
existing named based hierarchy. If we defines a type with "." separated
name like "httpd_t.php", toolchain implicitly set its bounds on "httpd_t".
This feature requires a new policy version.
The 24th version (POLICYDB_VERSION_BOUNDARY) enables to ship them into
kernel space, and the following patch enables to handle it.
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
This patch standardized the string auditing interfaces. No userspace
changes will be visible and this is all just cleanup and consistancy
work. We have the following string audit interfaces to use:
void audit_log_n_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len);
void audit_log_n_string(struct audit_buffer *ab, const char *buf, size_t n);
void audit_log_string(struct audit_buffer *ab, const char *buf);
void audit_log_n_untrustedstring(struct audit_buffer *ab, const char *string, size_t n);
void audit_log_untrustedstring(struct audit_buffer *ab, const char *string);
This may be the first step to possibly fixing some of the issues that
people have with the string output from the kernel audit system. But we
still don't have an agreed upon solution to that problem.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The attached patch needs to move from -rt to mainline given preemptable RCU.
This patch fixes SELinux code that implicitly assumes that disabling
preemption prevents an RCU grace period from completing, an assumption that
is valid for Classic RCU, but not necessarily for preemptable RCU. Explicit
rcu_read_lock() calls are thus added.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Eric Paris