| Message ID | 20170320094335.1266306-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote: > A struct file is a bit too large to put on the kernel stack in general > and triggers a warning for low settings of CONFIG_FRAME_WARN: > > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file': > drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free': > drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > > It's also slightly dangerous to leave a reference to a stack object > in the drm_file structure after leaving the stack frame. > This changes the code to just allocate the object dynamically > and release it when we are done with it. > > Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c > index 113dec05c7dc..18514065c93d 100644 > --- a/drivers/gpu/drm/i915/selftests/mock_drm.c > +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c > @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) > struct drm_file *mock_file(struct drm_i915_private *i915) > { > struct inode inode = fake_inode(i915); > - struct file filp = {}; > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); > struct drm_file *file; > int err; > > - err = drm_open(&inode, &filp); > + err = drm_open(&inode, filp); Aside: We should have a FIXME and/or merge David Herrmanns code to allow a drm_file without a real struct file for kernel-internal use ... -Daniel > if (unlikely(err)) > return ERR_PTR(err); > > - file = filp.private_data; > + file = filp->private_data; > file->authenticated = true; > return file; > } > @@ -48,7 +48,9 @@ struct drm_file *mock_file(struct drm_i915_private *i915) > void mock_file_free(struct drm_i915_private *i915, struct drm_file *file) > { > struct inode inode = fake_inode(i915); > - struct file filp = { .private_data = file }; > + struct file *filp = file->filp; > > - drm_release(&inode, &filp); > + drm_release(&inode, filp); > + > + kfree(filp); > } > -- > 2.9.0 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote: > A struct file is a bit too large to put on the kernel stack in general > and triggers a warning for low settings of CONFIG_FRAME_WARN: > > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file': > drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free': > drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > > It's also slightly dangerous to leave a reference to a stack object > in the drm_file structure after leaving the stack frame. > This changes the code to just allocate the object dynamically > and release it when we are done with it. > > Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> <SNIP> > --- > drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c > index 113dec05c7dc..18514065c93d 100644 > --- a/drivers/gpu/drm/i915/selftests/mock_drm.c > +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c > @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) > struct drm_file *mock_file(struct drm_i915_private *i915) > { > > struct inode inode = fake_inode(i915); > > - struct file filp = {}; > > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); > > struct drm_file *file; > > int err; > filp = kzalloc(sizeof(*filp), GFP_KERNEL); if (unlikely(!filp)) { err = -ENOMEM; goto err; } And appropriate onion teardown in case drm_open fails, so that we don't leak memory. Regards, Joonas
On Mon, Mar 20, 2017 at 1:00 PM, Joonas Lahtinen <joonas.lahtinen@linux.intel.com> wrote: > On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote: >> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c >> index 113dec05c7dc..18514065c93d 100644 >> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c >> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c >> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) >> struct drm_file *mock_file(struct drm_i915_private *i915) >> { >> > struct inode inode = fake_inode(i915); >> > - struct file filp = {}; >> > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); >> > struct drm_file *file; >> > int err; >> > > filp = kzalloc(sizeof(*filp), GFP_KERNEL); > if (unlikely(!filp)) { > err = -ENOMEM; > goto err; > } > > And appropriate onion teardown in case drm_open fails, so that we don't > leak memory. Oops, of course you are right, sorry about that. Arnd
On Mon, Mar 20, 2017 at 1:02 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Mon, Mar 20, 2017 at 1:00 PM, Joonas Lahtinen > <joonas.lahtinen@linux.intel.com> wrote: >> On ma, 2017-03-20 at 10:40 +0100, Arnd Bergmann wrote: > >>> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c >>> index 113dec05c7dc..18514065c93d 100644 >>> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c >>> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c >>> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) >>> struct drm_file *mock_file(struct drm_i915_private *i915) >>> { >>> > struct inode inode = fake_inode(i915); >>> > - struct file filp = {}; >>> > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); >>> > struct drm_file *file; >>> > int err; >>> >> >> filp = kzalloc(sizeof(*filp), GFP_KERNEL); >> if (unlikely(!filp)) { >> err = -ENOMEM; >> goto err; >> } >> >> And appropriate onion teardown in case drm_open fails, so that we don't >> leak memory. > > Oops, of course you are right, sorry about that. Actually it's even worse, as I had originally planned to also allocate the inode dynamically, but for some reasons didn't do that in the patch I sent. This version of the patch as I sent it is rather bogus, so please ignore it (but not the other two patches I sent). If David's solution to this problem can make it into 4.12, there is no problem at all. Another alternative would be to use anon_inode_getfile(), again with proper error handling and cleanup. This is a bit slower but gives us valid file and inode structures. Arnd
On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote: > A struct file is a bit too large to put on the kernel stack in general > and triggers a warning for low settings of CONFIG_FRAME_WARN: > > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file': > drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free': > drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > > It's also slightly dangerous to leave a reference to a stack object > in the drm_file structure after leaving the stack frame. > This changes the code to just allocate the object dynamically > and release it when we are done with it. > > Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c > index 113dec05c7dc..18514065c93d 100644 > --- a/drivers/gpu/drm/i915/selftests/mock_drm.c > +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c > @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) > struct drm_file *mock_file(struct drm_i915_private *i915) > { > struct inode inode = fake_inode(i915); > - struct file filp = {}; > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); > struct drm_file *file; > int err; > > - err = drm_open(&inode, &filp); > + err = drm_open(&inode, filp); > if (unlikely(err)) > return ERR_PTR(err); > > - file = filp.private_data; > + file = filp->private_data; What I don't like about this approach is that we leak the unwanted inode/file. We only want the drm_file here and any access to above that inside i915.ko is fubar. -Chris
diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c index 113dec05c7dc..18514065c93d 100644 --- a/drivers/gpu/drm/i915/selftests/mock_drm.c +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) struct drm_file *mock_file(struct drm_i915_private *i915) { struct inode inode = fake_inode(i915); - struct file filp = {}; + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); struct drm_file *file; int err; - err = drm_open(&inode, &filp); + err = drm_open(&inode, filp); if (unlikely(err)) return ERR_PTR(err); - file = filp.private_data; + file = filp->private_data; file->authenticated = true; return file; } @@ -48,7 +48,9 @@ struct drm_file *mock_file(struct drm_i915_private *i915) void mock_file_free(struct drm_i915_private *i915, struct drm_file *file) { struct inode inode = fake_inode(i915); - struct file filp = { .private_data = file }; + struct file *filp = file->filp; - drm_release(&inode, &filp); + drm_release(&inode, filp); + + kfree(filp); }
A struct file is a bit too large to put on the kernel stack in general and triggers a warning for low settings of CONFIG_FRAME_WARN: drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file': drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free': drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] It's also slightly dangerous to leave a reference to a stack object in the drm_file structure after leaving the stack frame. This changes the code to just allocate the object dynamically and release it when we are done with it. Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)