| Message ID | 1417505957-2666-4-git-send-email-famz@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Tue, 2 Dec 2014 15:39:14 +0800 Fam Zheng <famz@redhat.com> wrote: > Zeroing a buffer that will be filled right after is not necessary, and > allocating a power of two + 1 is naughty. > > Suggested-by: Markus Armbruster <armbru@redhat.com> > Signed-off-by: Fam Zheng <famz@redhat.com> > --- > block/vmdk.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/block/vmdk.c b/block/vmdk.c > index 28d22db..0c5769c 100644 > --- a/block/vmdk.c > +++ b/block/vmdk.c > @@ -558,14 +558,15 @@ static char *vmdk_read_desc(BlockDriverState *file, uint64_t desc_offset, > } > > size = MIN(size, 1 << 20); /* avoid unbounded allocation */ > - buf = g_malloc0(size + 1); > + buf = g_malloc(size); For a file that is less than 1<<20 bytes, won't this throw away the last byte? Maybe better is: size = MIN(size, (1 << 20) - 1); buf = g_malloc(size + 1); Leave the bdrv_pread as it was and... > > - ret = bdrv_pread(file, desc_offset, buf, size); > + ret = bdrv_pread(file, desc_offset, buf, size - 1); > if (ret < 0) { > error_setg_errno(errp, -ret, "Could not read from file"); > g_free(buf); > return NULL; > } > + buf[ret - 1] = 0; ...zero the last byte changes to: buf[ret] = 0; > > return buf; > } > -- > 1.9.3 -d
On Tue, 12/02 12:10, Don Koch wrote: > On Tue, 2 Dec 2014 15:39:14 +0800 > Fam Zheng <famz@redhat.com> wrote: > > > Zeroing a buffer that will be filled right after is not necessary, and > > allocating a power of two + 1 is naughty. > > > > Suggested-by: Markus Armbruster <armbru@redhat.com> > > Signed-off-by: Fam Zheng <famz@redhat.com> > > --- > > block/vmdk.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/block/vmdk.c b/block/vmdk.c > > index 28d22db..0c5769c 100644 > > --- a/block/vmdk.c > > +++ b/block/vmdk.c > > @@ -558,14 +558,15 @@ static char *vmdk_read_desc(BlockDriverState *file, uint64_t desc_offset, > > } > > > > size = MIN(size, 1 << 20); /* avoid unbounded allocation */ > > - buf = g_malloc0(size + 1); > > + buf = g_malloc(size); > > For a file that is less than 1<<20 bytes, won't this throw away the last byte? > Maybe better is: > size = MIN(size, (1 << 20) - 1); > buf = g_malloc(size + 1); > Leave the bdrv_pread as it was and... > > > > > - ret = bdrv_pread(file, desc_offset, buf, size); > > + ret = bdrv_pread(file, desc_offset, buf, size - 1); > > if (ret < 0) { > > error_setg_errno(errp, -ret, "Could not read from file"); > > g_free(buf); > > return NULL; > > } > > + buf[ret - 1] = 0; > > ...zero the last byte changes to: > buf[ret] = 0; Yes. I'll respin this one. Thanks. Fam > > > > > return buf; > > } > > -- > > 1.9.3 > > -d
diff --git a/block/vmdk.c b/block/vmdk.c index 28d22db..0c5769c 100644 --- a/block/vmdk.c +++ b/block/vmdk.c @@ -558,14 +558,15 @@ static char *vmdk_read_desc(BlockDriverState *file, uint64_t desc_offset, } size = MIN(size, 1 << 20); /* avoid unbounded allocation */ - buf = g_malloc0(size + 1); + buf = g_malloc(size); - ret = bdrv_pread(file, desc_offset, buf, size); + ret = bdrv_pread(file, desc_offset, buf, size - 1); if (ret < 0) { error_setg_errno(errp, -ret, "Could not read from file"); g_free(buf); return NULL; } + buf[ret - 1] = 0; return buf; }
Zeroing a buffer that will be filled right after is not necessary, and allocating a power of two + 1 is naughty. Suggested-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com> --- block/vmdk.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)