| Message ID | YNHXzBgzRrZu1MrD@miu.piliscsaba.redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ovl: fix mmap denywrite | expand |
Am 22.06.21 um 14:30 schrieb Miklos Szeredi: > Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE > mappings. Similarly negative i_mmap_writable counts were ignored for > VM_SHARED mappings. > > Fix by making vma_set_file() switch the temporary counts obtained and > released by mmap_region(). Mhm, I don't fully understand the background but that looks like something specific to overlayfs to me. So why are you changing the common helper? Thanks, Christian. > > Reported-by: Chengguang Xu <cgxu519@mykernel.net> > Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> > --- > fs/overlayfs/file.c | 4 +++- > include/linux/mm.h | 1 + > mm/mmap.c | 2 +- > mm/util.c | 38 +++++++++++++++++++++++++++++++++++++- > 4 files changed, 42 insertions(+), 3 deletions(-) > > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -430,7 +430,9 @@ static int ovl_mmap(struct file *file, s > if (WARN_ON(file != vma->vm_file)) > return -EIO; > > - vma_set_file(vma, realfile); > + ret = vma_set_file_checkwrite(vma, realfile); > + if (ret) > + return ret; > > old_cred = ovl_override_creds(file_inode(file)->i_sb); > ret = call_mmap(vma->vm_file, vma); > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2751,6 +2751,7 @@ static inline void vma_set_page_prot(str > #endif > > void vma_set_file(struct vm_area_struct *vma, struct file *file); > +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file); > > #ifdef CONFIG_NUMA_BALANCING > unsigned long change_prot_numa(struct vm_area_struct *vma, > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1809,6 +1809,7 @@ unsigned long mmap_region(struct file *f > */ > vma->vm_file = get_file(file); > error = call_mmap(file, vma); > + file = vma->vm_file; > if (error) > goto unmap_and_free_vma; > > @@ -1870,7 +1871,6 @@ unsigned long mmap_region(struct file *f > if (vm_flags & VM_DENYWRITE) > allow_write_access(file); > } > - file = vma->vm_file; > out: > perf_event_mmap(vma); > > --- a/mm/util.c > +++ b/mm/util.c > @@ -314,12 +314,48 @@ int vma_is_stack_for_current(struct vm_a > /* > * Change backing file, only valid to use during initial VMA setup. > */ > -void vma_set_file(struct vm_area_struct *vma, struct file *file) > +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file) > { > + vm_flags_t vm_flags = vma->vm_flags; > + int err = 0; > + > /* Changing an anonymous vma with this is illegal */ > get_file(file); > + > + /* Get temporary denial counts on replacement */ > + if (vm_flags & VM_DENYWRITE) { > + err = deny_write_access(file); > + if (err) > + goto out_put; > + } > + if (vm_flags & VM_SHARED) { > + err = mapping_map_writable(file->f_mapping); > + if (err) > + goto out_allow; > + } > + > swap(vma->vm_file, file); > + > + /* Undo temporary denial counts on replaced */ > + if (vm_flags & VM_SHARED) > + mapping_unmap_writable(file->f_mapping); > +out_allow: > + if (vm_flags & VM_DENYWRITE) > + allow_write_access(file); > +out_put: > fput(file); > + return err; > +} > +EXPORT_SYMBOL(vma_set_file_checkwrite); > + > +/* > + * Change backing file, only valid to use during initial VMA setup. > + */ > +void vma_set_file(struct vm_area_struct *vma, struct file *file) > +{ > + int err = vma_set_file_checkwrite(vma, file); > + > + WARN_ON_ONCE(err); > } > EXPORT_SYMBOL(vma_set_file); > > >
On Tue, 22 Jun 2021 at 14:43, Christian König <christian.koenig@amd.com> wrote: > > Am 22.06.21 um 14:30 schrieb Miklos Szeredi: > > Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE > > mappings. Similarly negative i_mmap_writable counts were ignored for > > VM_SHARED mappings. > > > > Fix by making vma_set_file() switch the temporary counts obtained and > > released by mmap_region(). > > Mhm, I don't fully understand the background but that looks like > something specific to overlayfs to me. > > So why are you changing the common helper? Need to hold the temporary counts until the final ones are obtained in vma_link(), which is out of overlayfs' scope. Thanks, Miklos
---- 在 星期二, 2021-06-22 20:30:04 Miklos Szeredi <miklos@szeredi.hu> 撰写 ---- > Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE > mappings. Similarly negative i_mmap_writable counts were ignored for > VM_SHARED mappings. > > Fix by making vma_set_file() switch the temporary counts obtained and > released by mmap_region(). > > Reported-by: Chengguang Xu <cgxu519@mykernel.net> > Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> > --- > fs/overlayfs/file.c | 4 +++- > include/linux/mm.h | 1 + > mm/mmap.c | 2 +- > mm/util.c | 38 +++++++++++++++++++++++++++++++++++++- > 4 files changed, 42 insertions(+), 3 deletions(-) > > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -430,7 +430,9 @@ static int ovl_mmap(struct file *file, s > if (WARN_ON(file != vma->vm_file)) > return -EIO; > > - vma_set_file(vma, realfile); > + ret = vma_set_file_checkwrite(vma, realfile); > + if (ret) > + return ret; I'm afraid that it may affect other overlayfs instances which share lower layers(no upper), so could we just check those permissions for upper layer? > > old_cred = ovl_override_creds(file_inode(file)->i_sb); > ret = call_mmap(vma->vm_file, vma); > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2751,6 +2751,7 @@ static inline void vma_set_page_prot(str > #endif > > void vma_set_file(struct vm_area_struct *vma, struct file *file); > +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file); > > #ifdef CONFIG_NUMA_BALANCING > unsigned long change_prot_numa(struct vm_area_struct *vma, > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1809,6 +1809,7 @@ unsigned long mmap_region(struct file *f > */ > vma->vm_file = get_file(file); > error = call_mmap(file, vma); > + file = vma->vm_file; I'm not sure the behavior of changing vma_file is always safe for vma merging case. In vma merging case, before go to tag 'unmap_writable' the reference of vma->vm_file will be released by fput(). For overlayfs, it probably safe because overlayfs file will get another reference for lower/upper file. Thanks, Chengguang Xu > if (error) > goto unmap_and_free_vma; > > @@ -1870,7 +1871,6 @@ unsigned long mmap_region(struct file *f > if (vm_flags & VM_DENYWRITE) > allow_write_access(file); > } > - file = vma->vm_file; > out: > perf_event_mmap(vma); > > --- a/mm/util.c > +++ b/mm/util.c > @@ -314,12 +314,48 @@ int vma_is_stack_for_current(struct vm_a > /* > * Change backing file, only valid to use during initial VMA setup. > */ > -void vma_set_file(struct vm_area_struct *vma, struct file *file) > +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file) > { > + vm_flags_t vm_flags = vma->vm_flags; > + int err = 0; > + > /* Changing an anonymous vma with this is illegal */ > get_file(file); > + > + /* Get temporary denial counts on replacement */ > + if (vm_flags & VM_DENYWRITE) { > + err = deny_write_access(file); > + if (err) > + goto out_put; > + } > + if (vm_flags & VM_SHARED) { > + err = mapping_map_writable(file->f_mapping); > + if (err) > + goto out_allow; > + } > + > swap(vma->vm_file, file); > + > + /* Undo temporary denial counts on replaced */ > + if (vm_flags & VM_SHARED) > + mapping_unmap_writable(file->f_mapping); > +out_allow: > + if (vm_flags & VM_DENYWRITE) > + allow_write_access(file); > +out_put: > fput(file); > + return err; > +} > +EXPORT_SYMBOL(vma_set_file_checkwrite); > + > +/* > + * Change backing file, only valid to use during initial VMA setup. > + */ > +void vma_set_file(struct vm_area_struct *vma, struct file *file) > +{ > + int err = vma_set_file_checkwrite(vma, file); > + > + WARN_ON_ONCE(err); > } > EXPORT_SYMBOL(vma_set_file); > > > >
Am 22.06.21 um 17:10 schrieb Miklos Szeredi: > On Tue, 22 Jun 2021 at 14:43, Christian König <christian.koenig@amd.com> wrote: >> Am 22.06.21 um 14:30 schrieb Miklos Szeredi: >>> Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE >>> mappings. Similarly negative i_mmap_writable counts were ignored for >>> VM_SHARED mappings. >>> >>> Fix by making vma_set_file() switch the temporary counts obtained and >>> released by mmap_region(). >> Mhm, I don't fully understand the background but that looks like >> something specific to overlayfs to me. >> >> So why are you changing the common helper? > Need to hold the temporary counts until the final ones are obtained in > vma_link(), which is out of overlayfs' scope. Ah! So basically we need to move the denial counts which mmap_region() added to the original file to the new one as well. That's indeed a rather good point. Can you rather change the vma_set_file() function to return the error and add a __must_check? I can take care fixing the users in DMA-buf and DRM subsystem. Thanks, Christian. > > Thanks, > Miklos
On Wed, Jun 23, 2021 at 01:41:02PM +0200, Christian König wrote: > > > Am 22.06.21 um 17:10 schrieb Miklos Szeredi: > > On Tue, 22 Jun 2021 at 14:43, Christian König <christian.koenig@amd.com> wrote: > > > Am 22.06.21 um 14:30 schrieb Miklos Szeredi: > > > > Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE > > > > mappings. Similarly negative i_mmap_writable counts were ignored for > > > > VM_SHARED mappings. > > > > > > > > Fix by making vma_set_file() switch the temporary counts obtained and > > > > released by mmap_region(). > > > Mhm, I don't fully understand the background but that looks like > > > something specific to overlayfs to me. > > > > > > So why are you changing the common helper? > > Need to hold the temporary counts until the final ones are obtained in > > vma_link(), which is out of overlayfs' scope. > > Ah! So basically we need to move the denial counts which mmap_region() added > to the original file to the new one as well. That's indeed a rather good > point. > > Can you rather change the vma_set_file() function to return the error and > add a __must_check? > > I can take care fixing the users in DMA-buf and DRM subsystem. Okay, but changing to __must_check has to be the last step to avoid compile errors. This v2 is with __must_check commented out. Thanks, Miklos --- From: Miklos Szeredi <mszeredi@redhat.com> Subject: [PATCH v2] ovl: fix mmap denywrite Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE mappings. Similarly negative i_mmap_writable counts were ignored for VM_SHARED mappings. Fix by making vma_set_file() switch the temporary counts obtained and released by mmap_region(). Reported-by: Chengguang Xu <cgxu519@mykernel.net> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/overlayfs/file.c | 4 +++- include/linux/mm.h | 2 +- mm/mmap.c | 2 +- mm/util.c | 27 ++++++++++++++++++++++++++- 4 files changed, 31 insertions(+), 4 deletions(-) --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -430,7 +430,9 @@ static int ovl_mmap(struct file *file, s if (WARN_ON(file != vma->vm_file)) return -EIO; - vma_set_file(vma, realfile); + ret = vma_set_file(vma, realfile); + if (ret) + return ret; old_cred = ovl_override_creds(file_inode(file)->i_sb); ret = call_mmap(vma->vm_file, vma); --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2776,7 +2776,7 @@ static inline void vma_set_page_prot(str } #endif -void vma_set_file(struct vm_area_struct *vma, struct file *file); +int /* __must_check */ vma_set_file(struct vm_area_struct *vma, struct file *file); #ifdef CONFIG_NUMA_BALANCING unsigned long change_prot_numa(struct vm_area_struct *vma, --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1807,6 +1807,7 @@ unsigned long mmap_region(struct file *f */ vma->vm_file = get_file(file); error = call_mmap(file, vma); + file = vma->vm_file; if (error) goto unmap_and_free_vma; @@ -1868,7 +1869,6 @@ unsigned long mmap_region(struct file *f if (vm_flags & VM_DENYWRITE) allow_write_access(file); } - file = vma->vm_file; out: perf_event_mmap(vma); --- a/mm/util.c +++ b/mm/util.c @@ -314,12 +314,37 @@ int vma_is_stack_for_current(struct vm_a /* * Change backing file, only valid to use during initial VMA setup. */ -void vma_set_file(struct vm_area_struct *vma, struct file *file) +int vma_set_file(struct vm_area_struct *vma, struct file *file) { + vm_flags_t vm_flags = vma->vm_flags; + int err = 0; + /* Changing an anonymous vma with this is illegal */ get_file(file); + + /* Get temporary denial counts on replacement */ + if (vm_flags & VM_DENYWRITE) { + err = deny_write_access(file); + if (err) + goto out_put; + } + if (vm_flags & VM_SHARED) { + err = mapping_map_writable(file->f_mapping); + if (err) + goto out_allow; + } + swap(vma->vm_file, file); + + /* Undo temporary denial counts on replaced */ + if (vm_flags & VM_SHARED) + mapping_unmap_writable(file->f_mapping); +out_allow: + if (vm_flags & VM_DENYWRITE) + allow_write_access(file); +out_put: fput(file); + return err; } EXPORT_SYMBOL(vma_set_file);
Am 09.07.21 um 15:48 schrieb Miklos Szeredi: > On Wed, Jun 23, 2021 at 01:41:02PM +0200, Christian König wrote: >> >> Am 22.06.21 um 17:10 schrieb Miklos Szeredi: >>> On Tue, 22 Jun 2021 at 14:43, Christian König <christian.koenig@amd.com> wrote: >>>> Am 22.06.21 um 14:30 schrieb Miklos Szeredi: >>>>> Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE >>>>> mappings. Similarly negative i_mmap_writable counts were ignored for >>>>> VM_SHARED mappings. >>>>> >>>>> Fix by making vma_set_file() switch the temporary counts obtained and >>>>> released by mmap_region(). >>>> Mhm, I don't fully understand the background but that looks like >>>> something specific to overlayfs to me. >>>> >>>> So why are you changing the common helper? >>> Need to hold the temporary counts until the final ones are obtained in >>> vma_link(), which is out of overlayfs' scope. >> Ah! So basically we need to move the denial counts which mmap_region() added >> to the original file to the new one as well. That's indeed a rather good >> point. >> >> Can you rather change the vma_set_file() function to return the error and >> add a __must_check? >> >> I can take care fixing the users in DMA-buf and DRM subsystem. > Okay, but changing to __must_check has to be the last step to avoid compile > errors. This v2 is with __must_check commented out. Good point. Please ping me whenever that is upstream and I will take care of fixing all the callers in the DRM subsystem and DMA-buf > > Thanks, > Miklos > --- > > From: Miklos Szeredi <mszeredi@redhat.com> > Subject: [PATCH v2] ovl: fix mmap denywrite > > Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE > mappings. Similarly negative i_mmap_writable counts were ignored for > VM_SHARED mappings. > > Fix by making vma_set_file() switch the temporary counts obtained and > released by mmap_region(). > > Reported-by: Chengguang Xu <cgxu519@mykernel.net> > Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Reviewed-by: Christian König <christian.koenig@amd.com> Regards, Christian. > --- > fs/overlayfs/file.c | 4 +++- > include/linux/mm.h | 2 +- > mm/mmap.c | 2 +- > mm/util.c | 27 ++++++++++++++++++++++++++- > 4 files changed, 31 insertions(+), 4 deletions(-) > > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -430,7 +430,9 @@ static int ovl_mmap(struct file *file, s > if (WARN_ON(file != vma->vm_file)) > return -EIO; > > - vma_set_file(vma, realfile); > + ret = vma_set_file(vma, realfile); > + if (ret) > + return ret; > > old_cred = ovl_override_creds(file_inode(file)->i_sb); > ret = call_mmap(vma->vm_file, vma); > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2776,7 +2776,7 @@ static inline void vma_set_page_prot(str > } > #endif > > -void vma_set_file(struct vm_area_struct *vma, struct file *file); > +int /* __must_check */ vma_set_file(struct vm_area_struct *vma, struct file *file); > > #ifdef CONFIG_NUMA_BALANCING > unsigned long change_prot_numa(struct vm_area_struct *vma, > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1807,6 +1807,7 @@ unsigned long mmap_region(struct file *f > */ > vma->vm_file = get_file(file); > error = call_mmap(file, vma); > + file = vma->vm_file; > if (error) > goto unmap_and_free_vma; > > @@ -1868,7 +1869,6 @@ unsigned long mmap_region(struct file *f > if (vm_flags & VM_DENYWRITE) > allow_write_access(file); > } > - file = vma->vm_file; > out: > perf_event_mmap(vma); > > --- a/mm/util.c > +++ b/mm/util.c > @@ -314,12 +314,37 @@ int vma_is_stack_for_current(struct vm_a > /* > * Change backing file, only valid to use during initial VMA setup. > */ > -void vma_set_file(struct vm_area_struct *vma, struct file *file) > +int vma_set_file(struct vm_area_struct *vma, struct file *file) > { > + vm_flags_t vm_flags = vma->vm_flags; > + int err = 0; > + > /* Changing an anonymous vma with this is illegal */ > get_file(file); > + > + /* Get temporary denial counts on replacement */ > + if (vm_flags & VM_DENYWRITE) { > + err = deny_write_access(file); > + if (err) > + goto out_put; > + } > + if (vm_flags & VM_SHARED) { > + err = mapping_map_writable(file->f_mapping); > + if (err) > + goto out_allow; > + } > + > swap(vma->vm_file, file); > + > + /* Undo temporary denial counts on replaced */ > + if (vm_flags & VM_SHARED) > + mapping_unmap_writable(file->f_mapping); > +out_allow: > + if (vm_flags & VM_DENYWRITE) > + allow_write_access(file); > +out_put: > fput(file); > + return err; > } > EXPORT_SYMBOL(vma_set_file); >
--- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -430,7 +430,9 @@ static int ovl_mmap(struct file *file, s if (WARN_ON(file != vma->vm_file)) return -EIO; - vma_set_file(vma, realfile); + ret = vma_set_file_checkwrite(vma, realfile); + if (ret) + return ret; old_cred = ovl_override_creds(file_inode(file)->i_sb); ret = call_mmap(vma->vm_file, vma); --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2751,6 +2751,7 @@ static inline void vma_set_page_prot(str #endif void vma_set_file(struct vm_area_struct *vma, struct file *file); +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file); #ifdef CONFIG_NUMA_BALANCING unsigned long change_prot_numa(struct vm_area_struct *vma, --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1809,6 +1809,7 @@ unsigned long mmap_region(struct file *f */ vma->vm_file = get_file(file); error = call_mmap(file, vma); + file = vma->vm_file; if (error) goto unmap_and_free_vma; @@ -1870,7 +1871,6 @@ unsigned long mmap_region(struct file *f if (vm_flags & VM_DENYWRITE) allow_write_access(file); } - file = vma->vm_file; out: perf_event_mmap(vma); --- a/mm/util.c +++ b/mm/util.c @@ -314,12 +314,48 @@ int vma_is_stack_for_current(struct vm_a /* * Change backing file, only valid to use during initial VMA setup. */ -void vma_set_file(struct vm_area_struct *vma, struct file *file) +int vma_set_file_checkwrite(struct vm_area_struct *vma, struct file *file) { + vm_flags_t vm_flags = vma->vm_flags; + int err = 0; + /* Changing an anonymous vma with this is illegal */ get_file(file); + + /* Get temporary denial counts on replacement */ + if (vm_flags & VM_DENYWRITE) { + err = deny_write_access(file); + if (err) + goto out_put; + } + if (vm_flags & VM_SHARED) { + err = mapping_map_writable(file->f_mapping); + if (err) + goto out_allow; + } + swap(vma->vm_file, file); + + /* Undo temporary denial counts on replaced */ + if (vm_flags & VM_SHARED) + mapping_unmap_writable(file->f_mapping); +out_allow: + if (vm_flags & VM_DENYWRITE) + allow_write_access(file); +out_put: fput(file); + return err; +} +EXPORT_SYMBOL(vma_set_file_checkwrite); + +/* + * Change backing file, only valid to use during initial VMA setup. + */ +void vma_set_file(struct vm_area_struct *vma, struct file *file) +{ + int err = vma_set_file_checkwrite(vma, file); + + WARN_ON_ONCE(err); } EXPORT_SYMBOL(vma_set_file);
Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE mappings. Similarly negative i_mmap_writable counts were ignored for VM_SHARED mappings. Fix by making vma_set_file() switch the temporary counts obtained and released by mmap_region(). Reported-by: Chengguang Xu <cgxu519@mykernel.net> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/overlayfs/file.c | 4 +++- include/linux/mm.h | 1 + mm/mmap.c | 2 +- mm/util.c | 38 +++++++++++++++++++++++++++++++++++++- 4 files changed, 42 insertions(+), 3 deletions(-)