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From: <pannengyuan@huawei.com>
To: <pbonzini@redhat.com>, <rth@twiddle.net>, <ehabkost@redhat.com>
Cc: qemu-trivial@nongnu.org, euler.robot@huawei.com,
	Pan Nengyuan <pannengyuan@huawei.com>,
	qemu-devel@nongnu.org, zhang.zhanghailiang@huawei.com
Subject: [PATCH] target/i386/hax-posix: fix two 'format-truncation' compile warnings
Date: Mon, 24 Feb 2020 14:51:39 +0800	[thread overview]
Message-ID: <20200224065139.19567-1-pannengyuan@huawei.com> (raw)

From: Pan Nengyuan <pannengyuan@huawei.com>

Fix compile warnings:
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:124:56: error: ‘%02d’ directive output may be truncated writing between 2 and 11 bytes into a region of size 3 [-Werror=format-truncation=]
     snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id);
                                                        ^~~~
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:124:41: note: directive argument in the range [-2147483648, 64]
     snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id);
                                         ^~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/stdio.h:873,
                 from /mnt/sdb/qemu-new/qemu_test/qemu/include/qemu/osdep.h:99,
                 from /mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:14:
/usr/include/bits/stdio2.h:67:10: note: ‘__builtin___snprintf_chk’ output between 17 and 26 bytes into a destination of size 17
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c: In function ‘hax_vcpu_devfs_string’:
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:143:55: error: ‘%02d’ directive output may be truncated writing between 2 and 11 bytes into a region of size 10 [-Werror=format-truncation=]
     snprintf(name, sizeof HAX_VCPU_DEVFS, "/dev/hax_vm%02d/vcpu%02d",
                                                       ^~~~
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:143:43: note: directive argument in the range [-2147483648, 64]
     snprintf(name, sizeof HAX_VCPU_DEVFS, "/dev/hax_vm%02d/vcpu%02d",
                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
/mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:143:43: note: directive argument in the range [-2147483648, 64]
In file included from /usr/include/stdio.h:873,
                 from /mnt/sdb/qemu-new/qemu_test/qemu/include/qemu/osdep.h:99,
                 from /mnt/sdb/qemu-new/qemu_test/qemu/target/i386/hax-posix.c:14:
/usr/include/bits/stdio2.h:67:10: note: ‘__builtin___snprintf_chk’ output between 21 and 39 bytes into a destination of size 21
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());

We know that we have checked the vm_id and vcpu_id in the first(less than 0x40), it will never be truncated in snprintf().
Thus, this patch add an assertion to clear this false-positive warning.

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
---
 target/i386/hax-posix.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/target/i386/hax-posix.c b/target/i386/hax-posix.c
index a5426a6dac..197d5bc0f9 100644
--- a/target/i386/hax-posix.c
+++ b/target/i386/hax-posix.c
@@ -121,7 +121,8 @@ static char *hax_vm_devfs_string(int vm_id)
         return NULL;
     }
 
-    snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id);
+    int len = snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id);
+    assert(len < sizeof HAX_VM_DEVFS);
     return name;
 }
 
@@ -140,8 +141,9 @@ static char *hax_vcpu_devfs_string(int vm_id, int vcpu_id)
         return NULL;
     }
 
-    snprintf(name, sizeof HAX_VCPU_DEVFS, "/dev/hax_vm%02d/vcpu%02d",
-             vm_id, vcpu_id);
+    int len = snprintf(name, sizeof HAX_VCPU_DEVFS, "/dev/hax_vm%02d/vcpu%02d",
+                       vm_id, vcpu_id);
+    assert(len < sizeof HAX_VCPU_DEVFS);
     return name;
 }
 
-- 
2.18.2



             reply	other threads:[~2020-02-24  6:36 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24  6:51 pannengyuan [this message]
2020-03-03 10:14 ` [PATCH] target/i386/hax-posix: fix two 'format-truncation' compile warnings Laurent Vivier
2020-03-03 10:47 ` Paolo Bonzini
2020-03-03 10:58   ` Pan Nengyuan

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