linux-stable.git/net/core/drop_monitor.c, branch v5.7

drop_monitor: work around gcc-10 stringop-overflow warning

2020-05-01T22:45:16+00:00

The current gcc-10 snapshot produces a false-positive warning:

net/core/drop_monitor.c: In function 'trace_drop_common.constprop':
cc1: error: writing 8 bytes into a region of size 0 [-Werror=stringop-overflow=]
In file included from net/core/drop_monitor.c:23:
include/uapi/linux/net_dropmon.h:36:8: note: at offset 0 to object 'entries' with size 4 declared here
   36 |  __u32 entries;
      |        ^~~~~~~

I reported this in the gcc bugzilla, but in case it does not get
fixed in the release, work around it by using a temporary variable.

Fixes: 9a8afc8d3962 ("Network Drop Monitor: Adding drop monitor implementation & Netlink protocol")
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94881
Signed-off-by: Arnd Bergmann 
Acked-by: Neil Horman 
Signed-off-by: David S. Miller

net: core: Replace zero-length array with flexible-array member

2020-02-28T20:08:37+00:00

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva 
Signed-off-by: David S. Miller

drop_monitor: extend by passing cookie from driver

2020-02-25T19:05:54+00:00

If driver passed along the cookie, push it through Netlink.

Signed-off-by: Jiri Pirko 
Signed-off-by: David S. Miller

drop_monitor: Do not cancel uninitialized work item

2020-02-07T17:48:36+00:00

Drop monitor uses a work item that takes care of constructing and
sending netlink notifications to user space. In case drop monitor never
started to monitor, then the work item is uninitialized and not
associated with a function.

Therefore, a stop command from user space results in canceling an
uninitialized work item which leads to the following warning [1].

Fix this by not processing a stop command if drop monitor is not
currently monitoring.

[1]
[   31.735402] ------------[ cut here ]------------
[   31.736470] WARNING: CPU: 0 PID: 143 at kernel/workqueue.c:3032 __flush_work+0x89f/0x9f0
...
[   31.738120] CPU: 0 PID: 143 Comm: dwdump Not tainted 5.5.0-custom-09491-g16d4077796b8 #727
[   31.741968] RIP: 0010:__flush_work+0x89f/0x9f0
...
[   31.760526] Call Trace:
[   31.771689]  __cancel_work_timer+0x2a6/0x3b0
[   31.776809]  net_dm_cmd_trace+0x300/0xef0
[   31.777549]  genl_rcv_msg+0x5c6/0xd50
[   31.781005]  netlink_rcv_skb+0x13b/0x3a0
[   31.784114]  genl_rcv+0x29/0x40
[   31.784720]  netlink_unicast+0x49f/0x6a0
[   31.787148]  netlink_sendmsg+0x7cf/0xc80
[   31.790426]  ____sys_sendmsg+0x620/0x770
[   31.793458]  ___sys_sendmsg+0xfd/0x170
[   31.802216]  __sys_sendmsg+0xdf/0x1a0
[   31.806195]  do_syscall_64+0xa0/0x540
[   31.806885]  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fixes: 8e94c3bc922e ("drop_monitor: Allow user to start monitoring hardware drops")
Signed-off-by: Ido Schimmel 
Reviewed-by: Jiri Pirko 
Signed-off-by: David S. Miller

net: drop_monitor: Use kstrdup

2020-01-30T09:03:37+00:00

Convert the equivalent but rather odd uses of kmemdup with
__GFP_ZERO to the more common kstrdup and avoid unnecessary
zeroing of copied over memory.

Signed-off-by: Joe Perches 
Signed-off-by: David S. Miller

drop_monitor: Better sanitize notified packets

2019-09-16T19:39:27+00:00

When working in 'packet' mode, drop monitor generates a notification
with a potentially truncated payload of the dropped packet. The payload
is copied from the MAC header, but I forgot to check that the MAC header
was set, so do it now.

Fixes: ca30707dee2b ("drop_monitor: Add packet alert mode")
Fixes: 5e58109b1ea4 ("drop_monitor: Add support for packet alert mode for hardware drops")
Acked-by: Jiri Pirko 
Signed-off-by: Ido Schimmel 
Signed-off-by: David S. Miller

drop_monitor: Make timestamps y2038 safe

2019-08-23T21:58:07+00:00

Timestamps are currently communicated to user space as 'struct
timespec', which is not considered y2038 safe since it uses a 32-bit
signed value for seconds.

Fix this while the API is still not part of any official kernel release
by using 64-bit nanoseconds timestamps instead.

Fixes: ca30707dee2b ("drop_monitor: Add packet alert mode")
Fixes: 5e58109b1ea4 ("drop_monitor: Add support for packet alert mode for hardware drops")
Signed-off-by: Ido Schimmel 
Acked-by: Neil Horman 
Signed-off-by: David S. Miller

drop_monitor: Allow user to start monitoring hardware drops

2019-08-17T19:40:08+00:00

Drop monitor has start and stop commands, but so far these were only
used to start and stop monitoring of software drops.

Now that drop monitor can also monitor hardware drops, we should allow
the user to control these as well.

Do that by adding SW and HW flags to these commands. If no flag is
specified, then only start / stop monitoring software drops. This is
done in order to maintain backward-compatibility with existing user
space applications.

Signed-off-by: Ido Schimmel 
Acked-by: Jiri Pirko 
Signed-off-by: David S. Miller

drop_monitor: Add support for summary alert mode for hardware drops

2019-08-17T19:40:08+00:00

In summary alert mode a notification is sent with a list of recent drop
reasons and a count of how many packets were dropped due to this reason.

To avoid expensive operations in the context in which packets are
dropped, each CPU holds an array whose number of entries is the maximum
number of drop reasons that can be encoded in the netlink notification.
Each entry stores the drop reason and a count. When a packet is dropped
the array is traversed and a new entry is created or the count of an
existing entry is incremented.

Later, in process context, the array is replaced with a newly allocated
copy and the old array is encoded in a netlink notification. To avoid
breaking user space, the notification includes the ancillary header,
which is 'struct net_dm_alert_msg' with number of entries set to '0'.

Signed-off-by: Ido Schimmel 
Acked-by: Jiri Pirko 
Signed-off-by: David S. Miller

drop_monitor: Add support for packet alert mode for hardware drops

2019-08-17T19:40:08+00:00

In a similar fashion to software drops, extend drop monitor to send
netlink events when packets are dropped by the underlying hardware.

The main difference is that instead of encoding the program counter (PC)
from which kfree_skb() was called in the netlink message, we encode the
hardware trap name. The two are mostly equivalent since they should both
help the user understand why the packet was dropped.

Signed-off-by: Ido Schimmel 
Acked-by: Jiri Pirko 
Signed-off-by: David S. Miller