linux.git/kernel/bpf, branch v4.12-rc2

bpf: adjust verifier heuristics

2017-05-18T02:55:27+00:00

Current limits with regards to processing program paths do not
really reflect today's needs anymore due to programs becoming
more complex and verifier smarter, keeping track of more data
such as const ALU operations, alignment tracking, spilling of
PTR_TO_MAP_VALUE_ADJ registers, and other features allowing for
smarter matching of what LLVM generates.

This also comes with the side-effect that we result in fewer
opportunities to prune search states and thus often need to do
more work to prove safety than in the past due to different
register states and stack layout where we mismatch. Generally,
it's quite hard to determine what caused a sudden increase in
complexity, it could be caused by something as trivial as a
single branch somewhere at the beginning of the program where
LLVM assigned a stack slot that is marked differently throughout
other branches and thus causing a mismatch, where verifier
then needs to prove safety for the whole rest of the program.
Subsequently, programs with even less than half the insn size
limit can get rejected. We noticed that while some programs
load fine under pre 4.11, they get rejected due to hitting
limits on more recent kernels. We saw that in the vast majority
of cases (90+%) pruning failed due to register mismatches. In
case of stack mismatches, majority of cases failed due to
different stack slot types (invalid, spill, misc) rather than
differences in spilled registers.

This patch makes pruning more aggressive by also adding markers
that sit at conditional jumps as well. Currently, we only mark
jump targets for pruning. For example in direct packet access,
these are usually error paths where we bail out. We found that
adding these markers, it can reduce number of processed insns
by up to 30%. Another option is to ignore reg->id in probing
PTR_TO_MAP_VALUE_OR_NULL registers, which can help pruning
slightly as well by up to 7% observed complexity reduction as
stand-alone. Meaning, if a previous path with register type
PTR_TO_MAP_VALUE_OR_NULL for map X was found to be safe, then
in the current state a PTR_TO_MAP_VALUE_OR_NULL register for
the same map X must be safe as well. Last but not least the
patch also adds a scheduling point and bumps the current limit
for instructions to be processed to a more adequate value.

Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: Handle multiple variable additions into packet pointers in verifier.

2017-05-12T02:48:58+00:00

We must accumulate into reg->aux_off rather than use a plain assignment.

Add a test for this situation to test_align.

Reported-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: Add strict alignment flag for BPF_PROG_LOAD.

2017-05-11T18:19:00+00:00

Add a new field, "prog_flags", and an initial flag value
BPF_F_STRICT_ALIGNMENT.

When set, the verifier will enforce strict pointer alignment
regardless of the setting of CONFIG_EFFICIENT_UNALIGNED_ACCESS.

The verifier, in this mode, will also use a fixed value of "2" in
place of NET_IP_ALIGN.

This facilitates test cases that will exercise and validate this part
of the verifier even when run on architectures where alignment doesn't
matter.

Signed-off-by: David S. Miller 
Acked-by: Daniel Borkmann

bpf: Do per-instruction state dumping in verifier when log_level > 1.

2017-05-11T18:19:00+00:00

If log_level > 1, do a state dump every instruction and emit it in
a more compact way (without a leading newline).

This will facilitate more sophisticated test cases which inspect the
verifier log for register state.

Signed-off-by: David S. Miller 
Acked-by: Daniel Borkmann

bpf: Track alignment of register values in the verifier.

2017-05-11T18:19:00+00:00

Currently if we add only constant values to pointers we can fully
validate the alignment, and properly check if we need to reject the
program on !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS architectures.

However, once an unknown value is introduced we only allow byte sized
memory accesses which is too restrictive.

Add logic to track the known minimum alignment of register values,
and propagate this state into registers containing pointers.

The most common paradigm that makes use of this new logic is computing
the transport header using the IP header length field.  For example:

	struct ethhdr *ep = skb->data;
	struct iphdr *iph = (struct iphdr *) (ep + 1);
	struct tcphdr *th;
 ...
	n = iph->ihl;
	th = ((void *)iph + (n * 4));
	port = th->dest;

The existing code will reject the load of th->dest because it cannot
validate that the alignment is at least 2 once "n * 4" is added the
the packet pointer.

In the new code, the register holding "n * 4" will have a reg->min_align
value of 4, because any value multiplied by 4 will be at least 4 byte
aligned.  (actually, the eBPF code emitted by the compiler in this case
is most likely to use a shift left by 2, but the end result is identical)

At the critical addition:

	th = ((void *)iph + (n * 4));

The register holding 'th' will start with reg->off value of 14.  The
pointer addition will transform that reg into something that looks like:

	reg->aux_off = 14
	reg->aux_off_align = 4

Next, the verifier will look at the th->dest load, and it will see
a load offset of 2, and first check:

	if (reg->aux_off_align % size)

which will pass because aux_off_align is 4.  reg_off will be computed:

	reg_off = reg->off;
 ...
		reg_off += reg->aux_off;

plus we have off==2, and it will thus check:

	if ((NET_IP_ALIGN + reg_off + off) % size != 0)

which evaluates to:

	if ((NET_IP_ALIGN + 14 + 2) % size != 0)

On strict alignment architectures, NET_IP_ALIGN is 2, thus:

	if ((2 + 14 + 2) % size != 0)

which passes.

These pointer transformations and checks work regardless of whether
the constant offset or the variable with known alignment is added
first to the pointer register.

Signed-off-by: David S. Miller 
Acked-by: Daniel Borkmann

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2017-05-09T22:42:31+00:00

Pull networking fixes from David Miller:

 1) Fix multiqueue in stmmac driver on PCI, from Andy Shevchenko.

 2) cdc_ncm doesn't actually fully zero out the padding area is
    allocates on TX, from Jim Baxter.

 3) Don't leak map addresses in BPF verifier, from Daniel Borkmann.

 4) If we randomize TCP timestamps, we have to do it everywhere
    including SYN cookies. From Eric Dumazet.

 5) Fix "ethtool -S" crash in aquantia driver, from Pavel Belous.

 6) Fix allocation size for ntp filter bitmap in bnxt_en driver, from
    Dan Carpenter.

 7) Add missing memory allocation return value check to DSA loop driver,
    from Christophe Jaillet.

 8) Fix XDP leak on driver unload in qed driver, from Suddarsana Reddy
    Kalluru.

 9) Don't inherit MC list from parent inet connection sockets, another
    syzkaller spotted gem. Fix from Eric Dumazet.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (43 commits)
  dccp/tcp: do not inherit mc_list from parent
  qede: Split PF/VF ndos.
  qed: Correct doorbell configuration for !4Kb pages
  qed: Tell QM the number of tasks
  qed: Fix VF removal sequence
  qede: Fix XDP memory leak on unload
  net/mlx4_core: Reduce harmless SRIOV error message to debug level
  net/mlx4_en: Avoid adding steering rules with invalid ring
  net/mlx4_en: Change the error print to debug print
  drivers: net: wimax: i2400m: i2400m-usb: Use time_after for time comparison
  DECnet: Use container_of() for embedded struct
  Revert "ipv4: restore rt->fi for reference counting"
  net: mdio-mux: bcm-iproc: call mdiobus_free() in error path
  net: ethernet: ti: cpsw: adjust cpsw fifos depth for fullduplex flow control
  ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf
  net: cdc_ncm: Fix TX zero padding
  stmmac: pci: split out common_default_data() helper
  stmmac: pci: RX queue routing configuration
  stmmac: pci: TX and RX queue priority configuration
  stmmac: pci: set default number of rx and tx queues
  ...

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2017-05-09T16:12:53+00:00

Pull misc vfs updates from Al Viro:
 "Assorted bits and pieces from various people. No common topic in this
  pile, sorry"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs/affs: add rename exchange
  fs/affs: add rename2 to prepare multiple methods
  Make stat/lstat/fstatat pass AT_NO_AUTOMOUNT to vfs_statx()
  fs: don't set *REFERENCED on single use objects
  fs: compat: Remove warning from COMPATIBLE_IOCTL
  remove pointless extern of atime_need_update_rcu()
  fs: completely ignore unknown open flags
  fs: add a VALID_OPEN_FLAGS
  fs: remove _submit_bh()
  fs: constify tree_descr arrays passed to simple_fill_super()
  fs: drop duplicate header percpu-rwsem.h
  fs/affs: bugfix: Write files greater than page size on OFS
  fs/affs: bugfix: enable writes on OFS disks
  fs/affs: remove node generation check
  fs/affs: import amigaffs.h
  fs/affs: bugfix: make symbolic links work again

mm, vmalloc: use __GFP_HIGHMEM implicitly

2017-05-09T00:15:13+00:00

__vmalloc* allows users to provide gfp flags for the underlying
allocation.  This API is quite popular

  $ git grep "=[[:space:]]__vmalloc\|return[[:space:]]*__vmalloc" | wc -l
  77

The only problem is that many people are not aware that they really want
to give __GFP_HIGHMEM along with other flags because there is really no
reason to consume precious lowmemory on CONFIG_HIGHMEM systems for pages
which are mapped to the kernel vmalloc space.  About half of users don't
use this flag, though.  This signals that we make the API unnecessarily
too complex.

This patch simply uses __GFP_HIGHMEM implicitly when allocating pages to
be mapped to the vmalloc space.  Current users which add __GFP_HIGHMEM
are simplified and drop the flag.

Link: http://lkml.kernel.org/r/20170307141020.29107-1-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reviewed-by: Matthew Wilcox 
Cc: Al Viro 
Cc: Vlastimil Babka 
Cc: David Rientjes 
Cc: Cristopher Lameter 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bpf: don't let ldimm64 leak map addresses on unprivileged

2017-05-08T19:06:46+00:00

The patch fixes two things at once:

1) It checks the env->allow_ptr_leaks and only prints the map address to
   the log if we have the privileges to do so, otherwise it just dumps 0
   as we would when kptr_restrict is enabled on %pK. Given the latter is
   off by default and not every distro sets it, I don't want to rely on
   this, hence the 0 by default for unprivileged.

2) Printing of ldimm64 in the verifier log is currently broken in that
   we don't print the full immediate, but only the 32 bit part of the
   first insn part for ldimm64. Thus, fix this up as well; it's okay to
   access, since we verified all ldimm64 earlier already (including just
   constants) through replace_map_fd_with_map_ptr().

Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")
Fixes: cbd357008604 ("bpf: verifier (add ability to receive verification log)")
Reported-by: Jann Horn 
Signed-off-by: Daniel Borkmann 
Acked-by: Alexei Starovoitov 
Signed-off-by: David S. Miller

bpf: enhance verifier to understand stack pointer arithmetic

2017-05-01T15:40:23+00:00

llvm 4.0 and above generates the code like below:
....
440: (b7) r1 = 15
441: (05) goto pc+73
515: (79) r6 = *(u64 *)(r10 -152)
516: (bf) r7 = r10
517: (07) r7 += -112
518: (bf) r2 = r7
519: (0f) r2 += r1
520: (71) r1 = *(u8 *)(r8 +0)
521: (73) *(u8 *)(r2 +45) = r1
....
and the verifier complains "R2 invalid mem access 'inv'" for insn #521.
This is because verifier marks register r2 as unknown value after #519
where r2 is a stack pointer and r1 holds a constant value.

Teach verifier to recognize "stack_ptr + imm" and
"stack_ptr + reg with const val" as valid stack_ptr with new offset.

Signed-off-by: Yonghong Song 
Acked-by: Martin KaFai Lau 
Acked-by: Daniel Borkmann 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: David S. Miller