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[PULL,05/15] linux-user: allocate heap memory for execve arguments

Message ID b936cb50aacf3cccf5d2363095c6547eb709583a.1496234766.git.riku.voipio@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Riku Voipio May 31, 2017, 1:08 p.m. UTC 
From: Prasad J Pandit <pjp@fedoraproject.org>

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 <jannh@google.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
---
 linux-user/syscall.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
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Patch

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 32aba195c5..c8f6efc89c 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7985,8 +7985,8 @@  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++) {
@@ -8047,6 +8047,9 @@  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: