On 12/3/19 12:01 PM, Marcelo Ricardo Leitner wrote:
On Tue, Dec 03, 2019 at 11:03:45AM -0500, Laura Abbott wrote:
The sizes for memcpy in flow_offload_mangle don't match
the source variables, leading to overflow errors on some
build configurations:
In function 'memcpy',
inlined from 'flow_offload_mangle' at net/netfilter/nf_flow_table_offload.c:112:2,
inlined from 'flow_offload_port_dnat' at net/netfilter/nf_flow_table_offload.c:373:2,
inlined from 'nf_flow_rule_route_ipv4' at net/netfilter/nf_flow_table_offload.c:424:3:
./include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
376 | __read_overflow2();
| ^~~~~~~~~~~~~~~~~~
make[2]: *** [scripts/Makefile.build:266: net/netfilter/nf_flow_table_offload.o] Error 1
Fix this by using the corresponding type.
Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
---
Seen on a Fedora powerpc little endian build with -O3 but it looks like
it is correctly catching an error with doing a memcpy outside the source
variable.
Hi,
It is right but the fix is not. In that call trace:
flow_offload_port_dnat() {
...
u32 mask = ~htonl(0xffff);
__be16 port;
...
flow_offload_mangle(entry, flow_offload_l4proto(flow), offset,
(u8 *)&port, (u8 *)&mask);
}
port should have a 32b storage as well, and aligned with the mask.
---
net/netfilter/nf_flow_table_offload.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index c54c9a6cc981..526f894d0bdb 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -108,8 +108,8 @@ static void flow_offload_mangle(struct flow_action_entry *entry,
entry->id = FLOW_ACTION_MANGLE;
entry->mangle.htype = htype;
entry->mangle.offset = offset;
- memcpy(&entry->mangle.mask, mask, sizeof(u32));
- memcpy(&entry->mangle.val, value, sizeof(u32));
^^^^^ ^^^ which is &port in the call above
+ memcpy(&entry->mangle.mask, mask, sizeof(u8));
+ memcpy(&entry->mangle.val, value, sizeof(u8));
This fix would cause it to copy only the first byte, which is not the
intention.
Thanks for the review. I took another look at fixing this and I
think it might be better for the maintainer or someone who is more
familiar with the code to fix this. I ended up down a rabbit
hole trying to get the types to work and I wasn't confident about
the casting.
Thanks,
Laura
}
static inline struct flow_action_entry *
--
2.21.0
