* [PATCH] dax: explain how read(2)/write(2) addresses are validated [not found] <CAGXu5jJqoegDg07vR0iRRV1U_qOpZx5eLbywEwD_sm-D7sQmdA@mail.gmail.com> @ 2017-08-16 17:36 ` Ross Zwisler 0 siblings, 0 replies; 6+ messages in thread From: Ross Zwisler @ 2017-08-16 17:36 UTC (permalink / raw) To: Andrew Morton, linux-kernel Cc: Mark Rutland, Jan Kara, Kees Cook, Matthew Wilcox, Will Deacon, linux-nvdimm, Dave Chinner, Christoph Hellwig, Alexander Viro, Catalin Marinas, linux-fsdevel, Robin Murphy Add a comment explaining how the user addresses provided to read(2) and write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() or copy_to_iter() on these without calling access_ok() first in the DAX code, and there was a concern that the user might be able to read/write to arbitrary kernel addresses with this path. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> --- Adding a comment instead of adding redundant access_ok() calls in the DAX code. If this is the wrong path to take, please let me know. fs/dax.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index 8c67517..2d50f32 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1060,6 +1060,11 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, if (map_len > end - pos) map_len = end - pos; + /* + * The userspace address for the memory copy has already been + * validated via access_ok() in either vfs_read() or + * vfs_write(), depending on which operation we are doing. + */ if (iov_iter_rw(iter) == WRITE) map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); -- 2.9.5 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm ^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] dax: explain how read(2)/write(2) addresses are validated @ 2017-08-16 17:36 ` Ross Zwisler 0 siblings, 0 replies; 6+ messages in thread From: Ross Zwisler @ 2017-08-16 17:36 UTC (permalink / raw) To: Andrew Morton, linux-kernel Cc: Ross Zwisler, Alexander Viro, Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara, Matthew Wilcox, linux-fsdevel, linux-nvdimm, Kees Cook, Will Deacon, Catalin Marinas, Robin Murphy, Mark Rutland Add a comment explaining how the user addresses provided to read(2) and write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() or copy_to_iter() on these without calling access_ok() first in the DAX code, and there was a concern that the user might be able to read/write to arbitrary kernel addresses with this path. Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> --- Adding a comment instead of adding redundant access_ok() calls in the DAX code. If this is the wrong path to take, please let me know. fs/dax.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/dax.c b/fs/dax.c index 8c67517..2d50f32 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1060,6 +1060,11 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, if (map_len > end - pos) map_len = end - pos; + /* + * The userspace address for the memory copy has already been + * validated via access_ok() in either vfs_read() or + * vfs_write(), depending on which operation we are doing. + */ if (iov_iter_rw(iter) == WRITE) map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); -- 2.9.5 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] dax: explain how read(2)/write(2) addresses are validated 2017-08-16 17:36 ` Ross Zwisler @ 2017-08-17 8:53 ` Jan Kara -1 siblings, 0 replies; 6+ messages in thread From: Jan Kara @ 2017-08-17 8:53 UTC (permalink / raw) To: Ross Zwisler Cc: Mark Rutland, Jan Kara, Kees Cook, Matthew Wilcox, Will Deacon, linux-nvdimm, Dave Chinner, linux-kernel, Alexander Viro, Catalin Marinas, linux-fsdevel, Andrew Morton, Robin Murphy, Christoph Hellwig On Wed 16-08-17 11:36:15, Ross Zwisler wrote: > Add a comment explaining how the user addresses provided to read(2) and > write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() > or copy_to_iter() on these without calling access_ok() first in the DAX > code, and there was a concern that the user might be able to read/write to > arbitrary kernel addresses with this path. > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Looks OK to me so feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Just I'd note that standard buffered read / write path is no different so I don't see a big point in adding this comment when it is not in any other path either... Honza > --- > > Adding a comment instead of adding redundant access_ok() calls in the DAX > code. If this is the wrong path to take, please let me know. > > fs/dax.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/dax.c b/fs/dax.c > index 8c67517..2d50f32 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1060,6 +1060,11 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > if (map_len > end - pos) > map_len = end - pos; > > + /* > + * The userspace address for the memory copy has already been > + * validated via access_ok() in either vfs_read() or > + * vfs_write(), depending on which operation we are doing. > + */ > if (iov_iter_rw(iter) == WRITE) > map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr, > map_len, iter); > -- > 2.9.5 > -- Jan Kara <jack@suse.com> SUSE Labs, CR _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] dax: explain how read(2)/write(2) addresses are validated @ 2017-08-17 8:53 ` Jan Kara 0 siblings, 0 replies; 6+ messages in thread From: Jan Kara @ 2017-08-17 8:53 UTC (permalink / raw) To: Ross Zwisler Cc: Andrew Morton, linux-kernel, Alexander Viro, Christoph Hellwig, Dan Williams, Dave Chinner, Jan Kara, Matthew Wilcox, linux-fsdevel, linux-nvdimm, Kees Cook, Will Deacon, Catalin Marinas, Robin Murphy, Mark Rutland On Wed 16-08-17 11:36:15, Ross Zwisler wrote: > Add a comment explaining how the user addresses provided to read(2) and > write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() > or copy_to_iter() on these without calling access_ok() first in the DAX > code, and there was a concern that the user might be able to read/write to > arbitrary kernel addresses with this path. > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Looks OK to me so feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Just I'd note that standard buffered read / write path is no different so I don't see a big point in adding this comment when it is not in any other path either... Honza > --- > > Adding a comment instead of adding redundant access_ok() calls in the DAX > code. If this is the wrong path to take, please let me know. > > fs/dax.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/dax.c b/fs/dax.c > index 8c67517..2d50f32 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -1060,6 +1060,11 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > if (map_len > end - pos) > map_len = end - pos; > > + /* > + * The userspace address for the memory copy has already been > + * validated via access_ok() in either vfs_read() or > + * vfs_write(), depending on which operation we are doing. > + */ > if (iov_iter_rw(iter) == WRITE) > map_len = dax_copy_from_iter(dax_dev, pgoff, kaddr, > map_len, iter); > -- > 2.9.5 > -- Jan Kara <jack@suse.com> SUSE Labs, CR ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] dax: explain how read(2)/write(2) addresses are validated 2017-08-17 8:53 ` Jan Kara @ 2017-08-17 15:20 ` Ross Zwisler -1 siblings, 0 replies; 6+ messages in thread From: Ross Zwisler @ 2017-08-17 15:20 UTC (permalink / raw) To: Jan Kara Cc: Mark Rutland, Andrew Morton, Matthew Wilcox, Will Deacon, linux-nvdimm, Dave Chinner, linux-kernel, Christoph Hellwig, Alexander Viro, Catalin Marinas, linux-fsdevel, Robin Murphy, Kees Cook On Thu, Aug 17, 2017 at 10:53:32AM +0200, Jan Kara wrote: > On Wed 16-08-17 11:36:15, Ross Zwisler wrote: > > Add a comment explaining how the user addresses provided to read(2) and > > write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() > > or copy_to_iter() on these without calling access_ok() first in the DAX > > code, and there was a concern that the user might be able to read/write to > > arbitrary kernel addresses with this path. > > > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > > Looks OK to me so feel free to add: > > Reviewed-by: Jan Kara <jack@suse.cz> > > Just I'd note that standard buffered read / write path is no different so I > don't see a big point in adding this comment when it is not in any other > path either... Fair enough. Yea, if it's not in any of the other paths either and it's just common knowledge that these addresses are validated at the VFS layer, we can leave it out. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] dax: explain how read(2)/write(2) addresses are validated @ 2017-08-17 15:20 ` Ross Zwisler 0 siblings, 0 replies; 6+ messages in thread From: Ross Zwisler @ 2017-08-17 15:20 UTC (permalink / raw) To: Jan Kara Cc: Ross Zwisler, Andrew Morton, linux-kernel, Alexander Viro, Christoph Hellwig, Dan Williams, Dave Chinner, Matthew Wilcox, linux-fsdevel, linux-nvdimm, Kees Cook, Will Deacon, Catalin Marinas, Robin Murphy, Mark Rutland On Thu, Aug 17, 2017 at 10:53:32AM +0200, Jan Kara wrote: > On Wed 16-08-17 11:36:15, Ross Zwisler wrote: > > Add a comment explaining how the user addresses provided to read(2) and > > write(2) are validated in the DAX I/O path. We call dax_copy_from_iter() > > or copy_to_iter() on these without calling access_ok() first in the DAX > > code, and there was a concern that the user might be able to read/write to > > arbitrary kernel addresses with this path. > > > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > > Looks OK to me so feel free to add: > > Reviewed-by: Jan Kara <jack@suse.cz> > > Just I'd note that standard buffered read / write path is no different so I > don't see a big point in adding this comment when it is not in any other > path either... Fair enough. Yea, if it's not in any of the other paths either and it's just common knowledge that these addresses are validated at the VFS layer, we can leave it out. ^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <CAGXu5jJqoegDg07vR0iRRV1U_qOpZx5eLbywEwD_sm-D7sQmdA@mail.gmail.com>
2017-08-16 17:36 ` [PATCH] dax: explain how read(2)/write(2) addresses are validated Ross Zwisler
2017-08-16 17:36 ` Ross Zwisler
2017-08-17 8:53 ` Jan Kara
2017-08-17 8:53 ` Jan Kara
2017-08-17 15:20 ` Ross Zwisler
2017-08-17 15:20 ` Ross Zwisler
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