[LTP] [PATCH v2] syscalls/sockioctl: Make buf a struct ifreq array

[Teo Couprie Diaz]

In setup3, the following line can lead to an undefined behavior:
  ifr = *(struct ifreq *)ifc.ifc_buf;

Indeed, at this point it can be assumed that ifc.ifc_buf is suitably
aligned for struct ifreq.
However, ifc.ifc_buf is assigned to buf, a char array, which has no
alignment constraints. This means there exists cases where buf is not
suitably aligned to load a struct ifreq, which can generate a SIGBUS.

Change buf from a char to a struct ifreq array, as it isn't used for
anything else in this test.
This guarantees that buff will be properly aligned.

Signed-off-by: Teo Couprie Diaz <teo.coupriediaz@arm.com>
---
I changed the cast from Cyril suggestion from (void*) to (char*) just
to be consistent with the type of (struct ifconf).ifc_buf.
>From my understanding this should be equivalent.

v2:
  - As per Cyril comments, make buf a struct ifreq array rather than
    align it with __attribute__
  - Update commit message accordingly

CI Build: https://github.com/Teo-CD/ltp/actions/runs/4531482995

 testcases/kernel/syscalls/sockioctl/sockioctl01.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/syscalls/sockioctl/sockioctl01.c b/testcases/kernel/syscalls/sockioctl/sockioctl01.c
index 51dac9c16309..ff3738f327ef 100644
--- a/testcases/kernel/syscalls/sockioctl/sockioctl01.c
+++ b/testcases/kernel/syscalls/sockioctl/sockioctl01.c
@@ -52,7 +52,7 @@ static struct ifreq ifr;
 static int sinlen;
 static int optval;
 
-static char buf[8192];
+static struct ifreq buf[200];
 
 static void setup(void);
 static void setup0(void);
@@ -218,7 +218,7 @@ static void setup2(void)
 	s = SAFE_SOCKET(cleanup, tdat[testno].domain, tdat[testno].type,
 			tdat[testno].proto);
 	ifc.ifc_len = sizeof(buf);
-	ifc.ifc_buf = buf;
+	ifc.ifc_buf = (char *)buf;
 }
 
 static void setup3(void)
-- 
2.34.1