Le 05/06/2025 à 16:46, Zhang He a écrit :
i write some bare-metal c code need mq_open/mq_unlink syscall, but
the syscall failed in passed name param check, arg1 in this scenario
is the correct address from user-space, arg1 - 1 not.
i have tested in arm cortex-m55 cpu model, maybe should add conditional compile
macro?
Signed-off-by: Zhang He <[email protected]>
---
linux-user/syscall.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index fc37028597..be9610176a 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -13058,7 +13058,7 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int
num, abi_long arg1,
}
pposix_mq_attr = &posix_mq_attr;
}
- p = lock_user_string(arg1 - 1);
+ p = lock_user_string(arg1);
if (!p) {
return -TARGET_EFAULT;
}
@@ -13068,7 +13068,7 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int
num, abi_long arg1,
return ret;
case TARGET_NR_mq_unlink:
- p = lock_user_string(arg1 - 1);
+ p = lock_user_string(arg1);
if (!p) {
return -TARGET_EFAULT;
}
According to the original thread:
Re: [Qemu-devel] [linux-user] Added posix message queue syscalls except
https://mail.gnu.org/archive/html/qemu-devel/2008-12/msg00966.html
It comes from glibc:
/* Remove message queue named NAME. */
int
__mq_unlink (const char *name)
{
if (name[0] != '/')
return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
int ret = INTERNAL_SYSCALL_CALL (mq_unlink, name + 1);
/* While unlink can return either EPERM or EACCES, mq_unlink should
return just EACCES. */
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (ret)))
{
ret = INTERNAL_SYSCALL_ERRNO (ret);
if (ret == EPERM)
ret = EACCES;
return INLINE_SYSCALL_ERROR_RETURN_VALUE (ret);
}
return ret;
}
I think the '+' is to remove the starting '/'.
So if we call it from linux-user app, the string is '/XXXX', then into
the linux-user glibc it becomes 'XXXX', so to pass it to the host glibc
again we need to restore the '/' by doing '- 1'.
So I don't think your change is correct.
Thanks,
Laurent
