| Message ID | 20220405103258.105701-1-mcascell@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | ui/cursor: fix integer overflow in cursor_alloc (CVE-2022-4206) | expand |
Hi On Tue, Apr 5, 2022 at 2:43 PM Mauro Matteo Cascella <mcascell@redhat.com> wrote: > Prevent potential integer overflow by limiting 'width' and 'height' to > 512x512. Also change 'datasize' type to size_t. Refer to security > advisory https://starlabs.sg/advisories/22-4206/ for more information. > > Fixes: CVE-2022-4206 > Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com> > --- > hw/display/qxl-render.c | 7 +++++++ > ui/cursor.c | 12 +++++++++++- > 2 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/hw/display/qxl-render.c b/hw/display/qxl-render.c > index d28849b121..dc3c4edd05 100644 > --- a/hw/display/qxl-render.c > +++ b/hw/display/qxl-render.c > @@ -247,6 +247,13 @@ static QEMUCursor *qxl_cursor(PCIQXLDevice *qxl, > QXLCursor *cursor, > size_t size; > > c = cursor_alloc(cursor->header.width, cursor->header.height); > + > + if (!c) { > + qxl_set_guest_bug(qxl, "%s: cursor %ux%u alloc error", __func__, > + cursor->header.width, cursor->header.height); > + goto fail; > + } > + > c->hot_x = cursor->header.hot_spot_x; > c->hot_y = cursor->header.hot_spot_y; > switch (cursor->header.type) { > diff --git a/ui/cursor.c b/ui/cursor.c > index 1d62ddd4d0..7cfb08a030 100644 > --- a/ui/cursor.c > +++ b/ui/cursor.c > @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) > > /* parse pixel data */ > c = cursor_alloc(width, height); > + > + if (!c) { > + fprintf(stderr, "%s: cursor %ux%u alloc error\n", > + __func__, width, height); > + return NULL; > + } > I think you could simply abort() in this function. It is used with static data (ui/cursor*.xpm) + > for (pixel = 0, y = 0; y < height; y++, line++) { > for (x = 0; x < height; x++, pixel++) { > idx = xpm[line][x]; > @@ -91,7 +98,10 @@ QEMUCursor *cursor_builtin_left_ptr(void) > QEMUCursor *cursor_alloc(int width, int height) > { > QEMUCursor *c; > - int datasize = width * height * sizeof(uint32_t); > + size_t datasize = width * height * sizeof(uint32_t); > + > + if (width > 512 || height > 512) > + return NULL; > > c = g_malloc0(sizeof(QEMUCursor) + datasize); > c->width = width; > -- > 2.35.1 > > > lgtm otherwise
> > +++ b/ui/cursor.c > > @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) > > > > /* parse pixel data */ > > c = cursor_alloc(width, height); > > + > > + if (!c) { > > + fprintf(stderr, "%s: cursor %ux%u alloc error\n", > > + __func__, width, height); > > + return NULL; > > + } > > > > I think you could simply abort() in this function. It is used with static > data (ui/cursor*.xpm) Yes, that should never happen. Missing: vmsvga_cursor_define() calls cursor_alloc() with guest-supplied values too. take care, Gerd
On Tue, 5 Apr 2022 at 11:50, Mauro Matteo Cascella <mcascell@redhat.com> wrote: > > Prevent potential integer overflow by limiting 'width' and 'height' to > 512x512. Also change 'datasize' type to size_t. Refer to security > advisory https://starlabs.sg/advisories/22-4206/ for more information. > > Fixes: CVE-2022-4206 > Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com> > diff --git a/ui/cursor.c b/ui/cursor.c > index 1d62ddd4d0..7cfb08a030 100644 > --- a/ui/cursor.c > +++ b/ui/cursor.c > @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) > > /* parse pixel data */ > c = cursor_alloc(width, height); > + > + if (!c) { > + fprintf(stderr, "%s: cursor %ux%u alloc error\n", > + __func__, width, height); > + return NULL; Side note, we should probably clean up the error handling in this file to not be "print to stderr" at some point... > + } > + > for (pixel = 0, y = 0; y < height; y++, line++) { > for (x = 0; x < height; x++, pixel++) { > idx = xpm[line][x]; > @@ -91,7 +98,10 @@ QEMUCursor *cursor_builtin_left_ptr(void) > QEMUCursor *cursor_alloc(int width, int height) > { > QEMUCursor *c; > - int datasize = width * height * sizeof(uint32_t); > + size_t datasize = width * height * sizeof(uint32_t); > + > + if (width > 512 || height > 512) > + return NULL; Coding style requires braces on if statements. thanks -- PMM
On Tue, Apr 5, 2022 at 1:10 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > > > +++ b/ui/cursor.c > > > @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) > > > > > > /* parse pixel data */ > > > c = cursor_alloc(width, height); > > > + > > > + if (!c) { > > > + fprintf(stderr, "%s: cursor %ux%u alloc error\n", > > > + __func__, width, height); > > > + return NULL; > > > + } > > > > > > > I think you could simply abort() in this function. It is used with static > > data (ui/cursor*.xpm) > > Yes, that should never happen. > > Missing: vmsvga_cursor_define() calls cursor_alloc() with guest-supplied > values too. I skipped that because the check (cursor.width > 256 || cursor.height > 256) is already done in vmsvga_fifo_run before calling vmsvga_cursor_define. You want me to add another check in vmsvga_cursor_define and return NULL if cursor_alloc fails? > take care, > Gerd > -- Mauro Matteo Cascella Red Hat Product Security PGP-Key ID: BB3410B0
On Tue, Apr 05, 2022 at 04:47:18PM +0200, Mauro Matteo Cascella wrote: > On Tue, Apr 5, 2022 at 1:10 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > > > > > +++ b/ui/cursor.c > > > > @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) > > > > > > > > /* parse pixel data */ > > > > c = cursor_alloc(width, height); > > > > + > > > > + if (!c) { > > > > + fprintf(stderr, "%s: cursor %ux%u alloc error\n", > > > > + __func__, width, height); > > > > + return NULL; > > > > + } > > > > > > > > > > I think you could simply abort() in this function. It is used with static > > > data (ui/cursor*.xpm) > > > > Yes, that should never happen. > > > > Missing: vmsvga_cursor_define() calls cursor_alloc() with guest-supplied > > values too. > > I skipped that because the check (cursor.width > 256 || cursor.height > > 256) is already done in vmsvga_fifo_run before calling > vmsvga_cursor_define. You want me to add another check in > vmsvga_cursor_define and return NULL if cursor_alloc fails? No check required then. Maybe add an 'assert(c != NULL)' to clarify this should never happen b/c those call sites never call cursor_alloc() with width/height being too big (your choice, applies to both vmsvga and ui/cursor.c). take care, Gerd
diff --git a/hw/display/qxl-render.c b/hw/display/qxl-render.c index d28849b121..dc3c4edd05 100644 --- a/hw/display/qxl-render.c +++ b/hw/display/qxl-render.c @@ -247,6 +247,13 @@ static QEMUCursor *qxl_cursor(PCIQXLDevice *qxl, QXLCursor *cursor, size_t size; c = cursor_alloc(cursor->header.width, cursor->header.height); + + if (!c) { + qxl_set_guest_bug(qxl, "%s: cursor %ux%u alloc error", __func__, + cursor->header.width, cursor->header.height); + goto fail; + } + c->hot_x = cursor->header.hot_spot_x; c->hot_y = cursor->header.hot_spot_y; switch (cursor->header.type) { diff --git a/ui/cursor.c b/ui/cursor.c index 1d62ddd4d0..7cfb08a030 100644 --- a/ui/cursor.c +++ b/ui/cursor.c @@ -46,6 +46,13 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[]) /* parse pixel data */ c = cursor_alloc(width, height); + + if (!c) { + fprintf(stderr, "%s: cursor %ux%u alloc error\n", + __func__, width, height); + return NULL; + } + for (pixel = 0, y = 0; y < height; y++, line++) { for (x = 0; x < height; x++, pixel++) { idx = xpm[line][x]; @@ -91,7 +98,10 @@ QEMUCursor *cursor_builtin_left_ptr(void) QEMUCursor *cursor_alloc(int width, int height) { QEMUCursor *c; - int datasize = width * height * sizeof(uint32_t); + size_t datasize = width * height * sizeof(uint32_t); + + if (width > 512 || height > 512) + return NULL; c = g_malloc0(sizeof(QEMUCursor) + datasize); c->width = width;
Prevent potential integer overflow by limiting 'width' and 'height' to 512x512. Also change 'datasize' type to size_t. Refer to security advisory https://starlabs.sg/advisories/22-4206/ for more information. Fixes: CVE-2022-4206 Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com> --- hw/display/qxl-render.c | 7 +++++++ ui/cursor.c | 12 +++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-)