[Qemu-devel] [PATCH v2 2/2] linux-user: allocate heap memory for execve arguments

[P J P]

From: Prasad J Pandit <address@hidden>

Arguments passed to execve(2) call from user program could
be large, allocating stack memory for them via alloca(3) call
would lead to bad behaviour. Use 'g_malloc0' to allocate memory
for such arguments.

Signed-off-by: Prasad J Pandit <address@hidden>
---
 linux-user/syscall.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Update per: replace alloca() with g_malloc0()
  -> https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg00750.html

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 86a4a9c..404fb0b 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7800,8 +7800,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                 ret = -TARGET_E2BIG;
                 break;
             }
-            argp = alloca((argc + 1) * sizeof(void *));
-            envp = alloca((envc + 1) * sizeof(void *));
+            argp = g_malloc0((argc + 1) * sizeof(void *));
+            envp = g_malloc0((envc + 1) * sizeof(void *));
 
             for (gp = guest_argp, q = argp; gp;
                   gp += sizeof(abi_ulong), q++) {
@@ -7862,6 +7862,9 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                     break;
                 unlock_user(*q, addr, 0);
             }
+
+            g_free(argp);
+            g_free(envp);
         }
         break;
     case TARGET_NR_chdir:
-- 
2.9.3