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dpif-linux: Avoid null dereference if all ports disappear.

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When dpif_linux_refresh_channels() refreshes the set of channels when
the number of handlers changes, it destroys all the dpif's channels and
sets dpif->uc_array_size to 0.  If the port dump later in the function
turns up no ports (which generally indicates a bug), then no channels will
be allocated and thus dpif->uc_array_size will remain 0 and 'channels' will
be null in each handler.  This is self-consistent, at least, but
dpif_linux_port_get_pid__() was still willing in this situation to
try to access element 0 of the set of channels, dereferencing a null
pointer.

This fixes the problem.

I encountered this while looking at a bug that I had introduced during
development that caused the port dump to always be empty.  It would be
difficult to encounter in normal use.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Joe Stringer <joestringer@nicira.com>
This commit is contained in:
Ben Pfaff
2014-07-14 13:17:05 -07:00
parent 2ffc8767e8
commit f8fc5489b6
1 changed files with 1 additions and 1 deletions
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lib/dpif-linux.c
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@@ -825,7 +825,7 @@ dpif_linux_port_get_pid__(const struct dpif_linux *dpif, odp_port_t port_no,
uint32_t port_idx = odp_to_u32(port_no);
uint32_t pid = 0;
if (dpif->handlers) {
if (dpif->handlers && dpif->uc_array_size > 0) {
/* The ODPP_NONE "reserved" port number uses the "ovs-system"'s
* channel, since it is not heavily loaded. */
uint32_t idx = port_idx >= dpif->uc_array_size ? 0 : port_idx;