| Message ID | 20200301163523.13581-1-jcfaracco@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | i386: Fix GCC warning with snprintf when HAX is enabled | expand |
On 3/1/20 8:35 AM, Julio Faracco wrote: > When HAX is enabled (--enable-hax), GCC 9.2.1 reports issues with > snprintf(). This commit is checking if snprintf returns an error. This > is a simple way to avoid this warnings. > > For more details, one example of warning: > CC i386-softmmu/target/i386/hax-posix.o > qemu/target/i386/hax-posix.c: In function ‘hax_host_open_vm’: > 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=] > 124 | snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id); > | ^~~~ > qemu/target/i386/hax-posix.c:124:41: note: directive argument in the range > [-2147483648, 64] The code bounds vm_id from the top (64) but not the bottom. The compiler has (correctly) determined that negative values will overflow your buffer. I suggest either an assert vs negative values as a local change, or to change the type of vm_id (universally, if possible) to an unsigned type. r~
diff --git a/target/i386/hax-posix.c b/target/i386/hax-posix.c index a5426a6dac..7437d54b44 100644 --- a/target/i386/hax-posix.c +++ b/target/i386/hax-posix.c @@ -121,7 +121,11 @@ static char *hax_vm_devfs_string(int vm_id) return NULL; } - snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id); + if (snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", + vm_id) < 0) { + return NULL; + } + return name; } @@ -140,8 +144,11 @@ 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); + if (snprintf(name, sizeof HAX_VCPU_DEVFS, "/dev/hax_vm%02d/vcpu%02d", + vm_id, vcpu_id) < 0) { + return NULL; + } + return name; }
When HAX is enabled (--enable-hax), GCC 9.2.1 reports issues with snprintf(). This commit is checking if snprintf returns an error. This is a simple way to avoid this warnings. For more details, one example of warning: CC i386-softmmu/target/i386/hax-posix.o qemu/target/i386/hax-posix.c: In function ‘hax_host_open_vm’: 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=] 124 | snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id); | ^~~~ qemu/target/i386/hax-posix.c:124:41: note: directive argument in the range [-2147483648, 64] 124 | snprintf(name, sizeof HAX_VM_DEVFS, "/dev/hax_vm/vm%02d", vm_id); | ^~~~~~~~~~~~~~~~~~~~ In file included from /usr/include/stdio.h:867, from qemu/include/qemu/osdep.h:99, from 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 67 | return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 68 | __bos (__s), __fmt, __va_arg_pack ()); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Signed-off-by: Julio Faracco <jcfaracco@gmail.com> --- target/i386/hax-posix.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)