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[Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_target_
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_target_sockaddr() |
Date: |
Thu, 7 Jul 2016 15:44:43 +0100 |
If userspace specifies a short buffer for a target sockaddr,
the kernel will only copy in as much as it has space for
(or none at all if the length is zero) -- see the kernel
move_addr_to_user() function. Mimic this in QEMU's
host_to_target_sockaddr() routine.
In particular, this fixes a segfault running the LTP
recvfrom01 test, where the guest makes a recvfrom()
call with a bad buffer pointer and other parameters which
cause the kernel to set the addrlen to zero; because we
did not skip the attempt to swap the sa_family field we
segfaulted on the bad address.
Signed-off-by: Peter Maydell <address@hidden>
---
linux-user/syscall.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 165fd06..6e77d34 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -1374,12 +1374,19 @@ static inline abi_long
host_to_target_sockaddr(abi_ulong target_addr,
{
struct target_sockaddr *target_saddr;
+ if (len == 0) {
+ return 0;
+ }
+
target_saddr = lock_user(VERIFY_WRITE, target_addr, len, 0);
if (!target_saddr)
return -TARGET_EFAULT;
memcpy(target_saddr, addr, len);
- target_saddr->sa_family = tswap16(addr->sa_family);
- if (addr->sa_family == AF_NETLINK) {
+ if (len >= offsetof(struct target_sockaddr, sa_family) +
+ sizeof(target_saddr->sa_family)) {
+ target_saddr->sa_family = tswap16(addr->sa_family);
+ }
+ if (addr->sa_family == AF_NETLINK && len >= sizeof(struct sockaddr_nl)) {
struct sockaddr_nl *target_nl = (struct sockaddr_nl *)target_saddr;
target_nl->nl_pid = tswap32(target_nl->nl_pid);
target_nl->nl_groups = tswap32(target_nl->nl_groups);
--
1.9.1
- [Qemu-devel] [PATCH] linux-user: Handle short lengths in host_to_target_sockaddr(),
Peter Maydell <=