[Qemu-devel] [PATCH v3] 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_new0' to allocate memory
for such arguments.

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

Update: use g_new0 instead of g_malloc0
  -> https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg01193.html

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index cec8428..c672581 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7926,8 +7926,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
                 envc++;
             }

-            argp = alloca((argc + 1) * sizeof(void *));
-            envp = alloca((envc + 1) * sizeof(void *));
+            argp = g_new0(char *, argc + 1);
+            envp = g_new0(char *, envc + 1);

             for (gp = guest_argp, q = argp; gp;
                   gp += sizeof(abi_ulong), q++) {
@@ -7988,6 +7988,9 @@ 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