Re: [PATCH] drm/vkms: fix use-after-free when drm_gem_handle_create() fails

From: Rodrigo Siqueira
Date: Sun Mar 10 2019 - 11:36:28 EST

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On 03/05, Dmitry Vyukov wrote:
> On Tue, Mar 5, 2019 at 12:23 AM Rodrigo Siqueira
> <rodrigosiqueiramelo@xxxxxxxxx> wrote:
> >
> > On 02/28, Dmitry Vyukov wrote:
> > > On Thu, Feb 28, 2019 at 12:12 AM Rodrigo Siqueira
> > > <rodrigosiqueiramelo@xxxxxxxxx> wrote:
> > > >
> > > > On 02/26, Eric Biggers wrote:
> > > > > From: Eric Biggers <ebiggers@xxxxxxxxxx>
> > > > >
> > > > > If drm_gem_handle_create() fails in vkms_gem_create(), then the
> > > > > vkms_gem_object is freed twice: once when the reference is dropped by
> > > > > drm_gem_object_put_unlocked(), and again by the extra calls to
> > > > > drm_gem_object_release() and kfree().
> > > > >
> > > > > Fix it by skipping the second release and free.
> > > > >
> > > > > This bug was originally found in the vgem driver by syzkaller using
> > > > > fault injection, but I noticed it's also present in the vkms driver.
> > > > >
> > > > > Fixes: 559e50fd34d1 ("drm/vkms: Add dumb operations")
> > > > > Cc: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
> > > > > Cc: Haneen Mohammed <hamohammed.sa@xxxxxxxxx>
> > > > > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > > > > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> > > > > ---
> > > > > drivers/gpu/drm/vkms/vkms_gem.c | 5 +----
> > > > > 1 file changed, 1 insertion(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
> > > > > index 138b0bb325cf9..69048e73377dc 100644
> > > > > --- a/drivers/gpu/drm/vkms/vkms_gem.c
> > > > > +++ b/drivers/gpu/drm/vkms/vkms_gem.c
> > > > > @@ -111,11 +111,8 @@ struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> > > > >
> > > > > ret = drm_gem_handle_create(file, &obj->gem, handle);
> > > > > drm_gem_object_put_unlocked(&obj->gem);
> > > > > - if (ret) {
> > > > > - drm_gem_object_release(&obj->gem);
> > > > > - kfree(obj);
> > > > > + if (ret)
> > > > > return ERR_PTR(ret);
> > > > > - }
> > > > >
> > > > > return &obj->gem;
> > > > > }
> > > > > --
> > > > > 2.21.0.rc2.261.ga7da99ff1b-goog
> > > > >
> > > >
> > > > Hi,
> > > >
> > > > Thanks for your patch! :)
> > > >
> > > > The patch looks good for me. I also tested it under the IGT tests on my
> > > > local VM and everything was fine.
> >
> > Hi,
> >
> > Patch applied to drm-misc-fixes.
> >
> > > Hi Rodrigo,
> > >
> > > What are IGT tests? How can I run them?
> >
> > Hi Dmitry,
> >
> > IGT is a test suite focused on DRM drivers.
> >
> > You can clone the project using the link below:
> >
> > https://gitlab.freedesktop.org/drm/igt-gpu-tools.git
> >
> > In the README, you will find the software dependencies. After you
> > install all the required package, just use:
> >
> > mkdir build && meson build && cd build && ninja
>
> Hi Rodrigo,
>
> Thanks for the info, but this did not work for me.
> I installed all recommended packages (including libdw-dev), but then got:

Hi Dmitry,

I would like to recommend you to join the dri-devel channel (Freenode).
There you can quickly get help from me and others ;)

My nick in the dri-devel is 'siqueira'.

Best Regards

> igt-gpu-tools$ mkdir -p build && meson build && cd build && ninja
> The Meson build system
> Version: 0.46.1
> Source dir: /src/igt-gpu-tools
> Build dir: /src/igt-gpu-tools/build
> Build type: native build
> Project name: igt-gpu-tools
> Native C compiler: ccache cc (gcc 7.3.0 "cc (Debian 7.3.0-5) 7.3.0")
> Build machine cpu family: x86_64
> Build machine cpu: x86_64
> Compiler for C supports arguments -Wbad-function-cast: YES
> Compiler for C supports arguments -Wdeclaration-after-statement: YES
> Compiler for C supports arguments -Wformat=2: YES
> Compiler for C supports arguments -Wimplicit-fallthrough=0: YES
> Compiler for C supports arguments -Wlogical-op: YES
> Compiler for C supports arguments -Wmissing-declarations: YES
> Compiler for C supports arguments -Wmissing-format-attribute: YES
> Compiler for C supports arguments -Wmissing-noreturn: YES
> Compiler for C supports arguments -Wmissing-prototypes: YES
> Compiler for C supports arguments -Wnested-externs: YES
> Compiler for C supports arguments -Wold-style-definition: YES
> Compiler for C supports arguments -Wpointer-arith: YES
> Compiler for C supports arguments -Wredundant-decls: YES
> Compiler for C supports arguments -Wshadow: YES
> Compiler for C supports arguments -Wstrict-prototypes: YES
> Compiler for C supports arguments -Wuninitialized: YES
> Compiler for C supports arguments -Wunused: YES
> Compiler for C supports arguments -Wno-clobbered -Wclobbered: YES
> Compiler for C supports arguments -Wno-maybe-uninitialized
> -Wmaybe-uninitialized: YES
> Compiler for C supports arguments -Wno-missing-field-initializers
> -Wmissing-field-initializers: YES
> Compiler for C supports arguments -Wno-pointer-arith -Wpointer-arith: YES
> Compiler for C supports arguments -Wno-sign-compare -Wsign-compare: YES
> Compiler for C supports arguments -Wno-type-limits -Wtype-limits: YES
> Compiler for C supports arguments -Wno-unused-parameter -Wunused-parameter: YES
> Compiler for C supports arguments -Wno-unused-result -Wunused-result: YES
> Compiler for C supports arguments -Werror=address: YES
> Compiler for C supports arguments -Werror=array-bounds: YES
> Compiler for C supports arguments -Werror=implicit: YES
> Compiler for C supports arguments -Werror=init-self: YES
> Compiler for C supports arguments -Werror=int-to-pointer-cast: YES
> Compiler for C supports arguments -Werror=main: YES
> Compiler for C supports arguments -Werror=missing-braces: YES
> Compiler for C supports arguments -Werror=nonnull: YES
> Compiler for C supports arguments -Werror=pointer-to-int-cast: YES
> Compiler for C supports arguments -Werror=return-type: YES
> Compiler for C supports arguments -Werror=sequence-point: YES
> Compiler for C supports arguments -Werror=trigraphs: YES
> Compiler for C supports arguments -Werror=write-strings: YES
> Found pkg-config: /usr/bin/pkg-config (0.29)
> Native dependency libdrm found: YES 2.4.91
> Native dependency libdrm_intel found: YES 2.4.91
> Native dependency libdrm_nouveau found: YES 2.4.91
> Native dependency libdrm_amdgpu found: YES 2.4.91
> Native dependency pciaccess found: YES 0.13.4
> Native dependency libkmod found: YES 24
> Native dependency libprocps found: YES 3.3.15
> Native dependency libunwind found: YES 1.21
>
> meson.build:151:0: ERROR: Could not generate cargs for libdw:
>
> A full log can be found at /src/igt-gpu-tools/build/meson-logs/meson-log.txt
>
>
> and meson-log.txt ends with:
>
> Compiler for C supports arguments -Werror=write-strings: YES
> Found pkg-config: /usr/bin/pkg-config (0.29)
> Determining dependency 'libdrm' with pkg-config executable '/usr/bin/pkg-config'
> Native dependency libdrm found: YES 2.4.91
> Determining dependency 'libdrm_intel' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libdrm_intel found: YES 2.4.91
> Determining dependency 'libdrm_nouveau' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libdrm_nouveau found: YES 2.4.91
> Determining dependency 'libdrm_amdgpu' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libdrm_amdgpu found: YES 2.4.91
> Determining dependency 'pciaccess' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency pciaccess found: YES 0.13.4
> Determining dependency 'libkmod' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libkmod found: YES 24
> Determining dependency 'libprocps' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libprocps found: YES 3.3.15
> Determining dependency 'libunwind' with pkg-config executable
> '/usr/bin/pkg-config'
> Native dependency libunwind found: YES 1.21
> Determining dependency 'libdw' with pkg-config executable '/usr/bin/pkg-config'
>
> meson.build:151:0: ERROR: Could not generate cargs for libdw:

--
Rodrigo Siqueira
https://siqueira.tech
Graduate Student
Department of Computer Science
University of São Paulo

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