| Message ID | a6010470b2d11f186cba89b9521940716fa66f3b.1721931241.git.josef@toxicpanda.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | fanotify: add pre-content hooks | expand |
On Thu 25-07-24 14:19:39, Josef Bacik wrote: > From: Amir Goldstein <amir73il@gmail.com> > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > but it meant for a different use case of filling file content before > access to a file range, so it has slightly different semantics. > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > FS_PRE_MODIFY is a new permission event, with similar semantics as > FS_PRE_ACCESS, which is called before a file is modified. > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > pre-content events are only reported for regular files and dirs. > > The pre-content events are meant to be used by hierarchical storage > managers that want to fill the content of files on first access. > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> The patch looks good. Just out of curiosity: > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > index 8be029bc50b1..21e72b837ec5 100644 > --- a/include/linux/fsnotify_backend.h > +++ b/include/linux/fsnotify_backend.h > @@ -56,6 +56,9 @@ > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ Why is a hole left here in the flag space? Honza
On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > From: Amir Goldstein <amir73il@gmail.com> > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > but it meant for a different use case of filling file content before > > access to a file range, so it has slightly different semantics. > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > FS_PRE_ACCESS, which is called before a file is modified. > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > pre-content events are only reported for regular files and dirs. > > > > The pre-content events are meant to be used by hierarchical storage > > managers that want to fill the content of files on first access. > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > The patch looks good. Just out of curiosity: > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > index 8be029bc50b1..21e72b837ec5 100644 > > --- a/include/linux/fsnotify_backend.h > > +++ b/include/linux/fsnotify_backend.h > > @@ -56,6 +56,9 @@ > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > Why is a hole left here in the flag space? Can't remember. Currently we have a draft design for two more events FS_PATH_ACCESS, FS_PATH_MODIFY https://github.com/amir73il/man-pages/commits/fan_pre_path So might have been a desire to keep the pre-events group on the nibble. Thanks, Amir.
On Sat, Aug 3, 2024 at 6:52 PM Amir Goldstein <amir73il@gmail.com> wrote: > > On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > > From: Amir Goldstein <amir73il@gmail.com> > > > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > > but it meant for a different use case of filling file content before > > > access to a file range, so it has slightly different semantics. > > > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > > FS_PRE_ACCESS, which is called before a file is modified. > > > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > > pre-content events are only reported for regular files and dirs. > > > > > > The pre-content events are meant to be used by hierarchical storage > > > managers that want to fill the content of files on first access. > > > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > > > The patch looks good. Just out of curiosity: > > > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > > index 8be029bc50b1..21e72b837ec5 100644 > > > --- a/include/linux/fsnotify_backend.h > > > +++ b/include/linux/fsnotify_backend.h > > > @@ -56,6 +56,9 @@ > > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > > > Why is a hole left here in the flag space? > > Can't remember. > > Currently we have a draft design for two more events > FS_PATH_ACCESS, FS_PATH_MODIFY > https://github.com/amir73il/man-pages/commits/fan_pre_path > > So might have been a desire to keep the pre-events group on the nibble. Funny story. I straced a program with latest FS_PRE_ACCESS (0x00080000) and see what I got: fanotify_mark(3, FAN_MARK_ADD|FAN_MARK_MOUNT, FAN_CLOSE_WRITE|FAN_OPEN_PERM|FAN_ACCESS_PERM|FAN_DIR_MODIFY|FAN_ONDIR, AT_FDCWD, "/vdd") = 0 "FAN_DIR_MODIFY"! a blast from the past [1] It would have been nice if we reserved 0x00080000 for FAN_PATH_MODIFY [2] to be a bit less confusing for users with old strace. WDYT? Thanks, Amir. [1] https://lore.kernel.org/linux-fsdevel/20200612093343.5669-18-amir73il@gmail.com/ [2] https://github.com/amir73il/man-pages/commits/fan_pre_path
On Fri 25-10-24 09:55:21, Amir Goldstein wrote: > On Sat, Aug 3, 2024 at 6:52 PM Amir Goldstein <amir73il@gmail.com> wrote: > > On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > > > From: Amir Goldstein <amir73il@gmail.com> > > > > > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > > > but it meant for a different use case of filling file content before > > > > access to a file range, so it has slightly different semantics. > > > > > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > > > FS_PRE_ACCESS, which is called before a file is modified. > > > > > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > > > pre-content events are only reported for regular files and dirs. > > > > > > > > The pre-content events are meant to be used by hierarchical storage > > > > managers that want to fill the content of files on first access. > > > > > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > > > > > The patch looks good. Just out of curiosity: > > > > > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > > > index 8be029bc50b1..21e72b837ec5 100644 > > > > --- a/include/linux/fsnotify_backend.h > > > > +++ b/include/linux/fsnotify_backend.h > > > > @@ -56,6 +56,9 @@ > > > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > > > > > Why is a hole left here in the flag space? > > > > Can't remember. > > > > Currently we have a draft design for two more events > > FS_PATH_ACCESS, FS_PATH_MODIFY > > https://github.com/amir73il/man-pages/commits/fan_pre_path > > > > So might have been a desire to keep the pre-events group on the nibble. > > Funny story. > > I straced a program with latest FS_PRE_ACCESS (0x00080000) and > see what I got: > > fanotify_mark(3, FAN_MARK_ADD|FAN_MARK_MOUNT, > FAN_CLOSE_WRITE|FAN_OPEN_PERM|FAN_ACCESS_PERM|FAN_DIR_MODIFY|FAN_ONDIR, > AT_FDCWD, "/vdd") = 0 > > "FAN_DIR_MODIFY"! a blast from the past [1] > > It would have been nice if we reserved 0x00080000 for FAN_PATH_MODIFY [2] > to be a bit less confusing for users with old strace. > > WDYT? Yeah, reusing that bit for something semantically close would reduce some confusion. But realistically I don't think FAN_DIR_MODIFY go wide use when it was never supported in a released upstream kernel. Honza
On Fri, Oct 25, 2024 at 3:09 PM Jan Kara <jack@suse.cz> wrote: > > On Fri 25-10-24 09:55:21, Amir Goldstein wrote: > > On Sat, Aug 3, 2024 at 6:52 PM Amir Goldstein <amir73il@gmail.com> wrote: > > > On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > > > > From: Amir Goldstein <amir73il@gmail.com> > > > > > > > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > > > > but it meant for a different use case of filling file content before > > > > > access to a file range, so it has slightly different semantics. > > > > > > > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > > > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > > > > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > > > > FS_PRE_ACCESS, which is called before a file is modified. > > > > > > > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > > > > pre-content events are only reported for regular files and dirs. > > > > > > > > > > The pre-content events are meant to be used by hierarchical storage > > > > > managers that want to fill the content of files on first access. > > > > > > > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > > > > > > > The patch looks good. Just out of curiosity: > > > > > > > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > > > > index 8be029bc50b1..21e72b837ec5 100644 > > > > > --- a/include/linux/fsnotify_backend.h > > > > > +++ b/include/linux/fsnotify_backend.h > > > > > @@ -56,6 +56,9 @@ > > > > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > > > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > > > > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > > > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > > > > > > > Why is a hole left here in the flag space? > > > > > > Can't remember. > > > > > > Currently we have a draft design for two more events > > > FS_PATH_ACCESS, FS_PATH_MODIFY > > > https://github.com/amir73il/man-pages/commits/fan_pre_path > > > > > > So might have been a desire to keep the pre-events group on the nibble. > > > > Funny story. > > > > I straced a program with latest FS_PRE_ACCESS (0x00080000) and > > see what I got: > > > > fanotify_mark(3, FAN_MARK_ADD|FAN_MARK_MOUNT, > > FAN_CLOSE_WRITE|FAN_OPEN_PERM|FAN_ACCESS_PERM|FAN_DIR_MODIFY|FAN_ONDIR, > > AT_FDCWD, "/vdd") = 0 > > > > "FAN_DIR_MODIFY"! a blast from the past [1] > > > > It would have been nice if we reserved 0x00080000 for FAN_PATH_MODIFY [2] > > to be a bit less confusing for users with old strace. > > > > WDYT? > > Yeah, reusing that bit for something semantically close would reduce some > confusion. But realistically I don't think FAN_DIR_MODIFY go wide use when > it was never supported in a released upstream kernel. No, but its legacy lives in strace forever... Anyway I included a patch in my fan_pre_access branch to reserve this bit because what have we got to loose.. Thanks, Amir.
On Fri, Oct 25, 2024 at 3:39 PM Amir Goldstein <amir73il@gmail.com> wrote: > > On Fri, Oct 25, 2024 at 3:09 PM Jan Kara <jack@suse.cz> wrote: > > > > On Fri 25-10-24 09:55:21, Amir Goldstein wrote: > > > On Sat, Aug 3, 2024 at 6:52 PM Amir Goldstein <amir73il@gmail.com> wrote: > > > > On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > > > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > > > > > From: Amir Goldstein <amir73il@gmail.com> > > > > > > > > > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > > > > > but it meant for a different use case of filling file content before > > > > > > access to a file range, so it has slightly different semantics. > > > > > > > > > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > > > > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > > > > > > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > > > > > FS_PRE_ACCESS, which is called before a file is modified. > > > > > > > > > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > > > > > pre-content events are only reported for regular files and dirs. > > > > > > > > > > > > The pre-content events are meant to be used by hierarchical storage > > > > > > managers that want to fill the content of files on first access. > > > > > > > > > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > > > > > > > > > The patch looks good. Just out of curiosity: > > > > > > > > > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > > > > > index 8be029bc50b1..21e72b837ec5 100644 > > > > > > --- a/include/linux/fsnotify_backend.h > > > > > > +++ b/include/linux/fsnotify_backend.h > > > > > > @@ -56,6 +56,9 @@ > > > > > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > > > > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > > > > > > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > > > > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > > > > > > > > > Why is a hole left here in the flag space? > > > > > > > > Can't remember. > > > > > > > > Currently we have a draft design for two more events > > > > FS_PATH_ACCESS, FS_PATH_MODIFY > > > > https://github.com/amir73il/man-pages/commits/fan_pre_path > > > > > > > > So might have been a desire to keep the pre-events group on the nibble. > > > > > > Funny story. > > > > > > I straced a program with latest FS_PRE_ACCESS (0x00080000) and > > > see what I got: > > > > > > fanotify_mark(3, FAN_MARK_ADD|FAN_MARK_MOUNT, > > > FAN_CLOSE_WRITE|FAN_OPEN_PERM|FAN_ACCESS_PERM|FAN_DIR_MODIFY|FAN_ONDIR, > > > AT_FDCWD, "/vdd") = 0 > > > > > > "FAN_DIR_MODIFY"! a blast from the past [1] > > > > > > It would have been nice if we reserved 0x00080000 for FAN_PATH_MODIFY [2] > > > to be a bit less confusing for users with old strace. > > > > > > WDYT? > > > > Yeah, reusing that bit for something semantically close would reduce some > > confusion. But realistically I don't think FAN_DIR_MODIFY go wide use when > > it was never supported in a released upstream kernel. > > No, but its legacy lives in strace forever... > Speaking of legacy events, you will notice that in the fan_pre_access branch I swapped the order of FS_PRE_ACCESS to be generated before FS_ACCESS_PERM. It is a semantic difference that probably does not matter much in practice, but I justified it as "need to fill the content before content can be inspected" because FS_ACCESS_PERM is the legacy Anti-malware event. This order is also aligned with the priority group associated with those events (PRE_CONTENT before CONTENT). But from a wider POV, my feeling is that FS_ACCESS_PERM is not really used by anyone and it is baggage that we need to try to get rid of. It is not worth the bloat of the inlined fsnotify_file_area_perm() hook. It is not worth the wasted cycles in the __fsnotify_parent() call that will not be optimized when there is any high priority group listener on the sb. I am tempted to try and combine the PRE/PERM access events into a single event and make sure that no fanotify group can subscribe to both of them at the same time, so a combined event can never be seen, but it is not very easy to rationalize this API. For example, if we would have required FAN_REPORT_RANGE init flag for subscribing to FAN_PRE_ACCESS, then we could have denied the legacy FAN_ACCESS_PERM in this group, but I don't think that we want to do that (?). WDYT? Am I overthinking again? Thanks, Amir.
On Sat 26-10-24 08:58:47, Amir Goldstein wrote: > On Fri, Oct 25, 2024 at 3:39 PM Amir Goldstein <amir73il@gmail.com> wrote: > > > > On Fri, Oct 25, 2024 at 3:09 PM Jan Kara <jack@suse.cz> wrote: > > > > > > On Fri 25-10-24 09:55:21, Amir Goldstein wrote: > > > > On Sat, Aug 3, 2024 at 6:52 PM Amir Goldstein <amir73il@gmail.com> wrote: > > > > > On Thu, Aug 1, 2024 at 6:31 PM Jan Kara <jack@suse.cz> wrote: > > > > > > On Thu 25-07-24 14:19:39, Josef Bacik wrote: > > > > > > > From: Amir Goldstein <amir73il@gmail.com> > > > > > > > > > > > > > > The new FS_PRE_ACCESS permission event is similar to FS_ACCESS_PERM, > > > > > > > but it meant for a different use case of filling file content before > > > > > > > access to a file range, so it has slightly different semantics. > > > > > > > > > > > > > > Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events, same as > > > > > > > we did for FS_OPEN_PERM/FS_OPEN_EXEC_PERM. > > > > > > > > > > > > > > FS_PRE_MODIFY is a new permission event, with similar semantics as > > > > > > > FS_PRE_ACCESS, which is called before a file is modified. > > > > > > > > > > > > > > FS_ACCESS_PERM is reported also on blockdev and pipes, but the new > > > > > > > pre-content events are only reported for regular files and dirs. > > > > > > > > > > > > > > The pre-content events are meant to be used by hierarchical storage > > > > > > > managers that want to fill the content of files on first access. > > > > > > > > > > > > > > Signed-off-by: Amir Goldstein <amir73il@gmail.com> > > > > > > > > > > > > The patch looks good. Just out of curiosity: > > > > > > > > > > > > > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h > > > > > > > index 8be029bc50b1..21e72b837ec5 100644 > > > > > > > --- a/include/linux/fsnotify_backend.h > > > > > > > +++ b/include/linux/fsnotify_backend.h > > > > > > > @@ -56,6 +56,9 @@ > > > > > > > #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ > > > > > > > #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ > > > > > > > > > > > > > > +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ > > > > > > > +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ > > > > > > > > > > > > Why is a hole left here in the flag space? > > > > > > > > > > Can't remember. > > > > > > > > > > Currently we have a draft design for two more events > > > > > FS_PATH_ACCESS, FS_PATH_MODIFY > > > > > https://github.com/amir73il/man-pages/commits/fan_pre_path > > > > > > > > > > So might have been a desire to keep the pre-events group on the nibble. > > > > > > > > Funny story. > > > > > > > > I straced a program with latest FS_PRE_ACCESS (0x00080000) and > > > > see what I got: > > > > > > > > fanotify_mark(3, FAN_MARK_ADD|FAN_MARK_MOUNT, > > > > FAN_CLOSE_WRITE|FAN_OPEN_PERM|FAN_ACCESS_PERM|FAN_DIR_MODIFY|FAN_ONDIR, > > > > AT_FDCWD, "/vdd") = 0 > > > > > > > > "FAN_DIR_MODIFY"! a blast from the past [1] > > > > > > > > It would have been nice if we reserved 0x00080000 for FAN_PATH_MODIFY [2] > > > > to be a bit less confusing for users with old strace. > > > > > > > > WDYT? > > > > > > Yeah, reusing that bit for something semantically close would reduce some > > > confusion. But realistically I don't think FAN_DIR_MODIFY go wide use when > > > it was never supported in a released upstream kernel. > > > > No, but its legacy lives in strace forever... > > > > Speaking of legacy events, you will notice that in the fan_pre_access > branch I swapped the order of FS_PRE_ACCESS to be generated > before FS_ACCESS_PERM. > > It is a semantic difference that probably does not matter much in practice, > but I justified it as "need to fill the content before content can be inspected" > because FS_ACCESS_PERM is the legacy Anti-malware event. > > This order is also aligned with the priority group associated with those > events (PRE_CONTENT before CONTENT). Yes, I've noticed this and it makes sense. Thanks for the expanded rationale. > But from a wider POV, my feeling is that FS_ACCESS_PERM is not > really used by anyone and it is baggage that we need to try to get rid of. > It is not worth the bloat of the inlined fsnotify_file_area_perm() hook. > It is not worth the wasted cycles in the __fsnotify_parent() call that will > not be optimized when there is any high priority group listener on the sb. > > I am tempted to try and combine the PRE/PERM access events into > a single event and make sure that no fanotify group can subscribe to > both of them at the same time, so a combined event can never be seen, > but it is not very easy to rationalize this API. > > For example, if we would have required FAN_REPORT_RANGE init flag > for subscribing to FAN_PRE_ACCESS, then we could have denied the legacy > FAN_ACCESS_PERM in this group, but I don't think that we want to do that (?). Yeah, this would look a bit weird in the API. If you really think that FAN_ACCESS_PERM is dead (which it may well be but I would not bet on it), then we could start a deprecation period for it and if nobody comes back to us saying they still use it, we can then remove it from the kernel altogether. Honza
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 272c8a1dab3c..1ca4a8da7f29 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -621,7 +621,7 @@ static __init int fsnotify_init(void) { int ret; - BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23); + BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25); ret = init_srcu_struct(&fsnotify_mark_srcu); if (ret) diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 278620e063ab..028ce807805a 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -133,12 +133,13 @@ static inline int fsnotify_file(struct file *file, __u32 mask) #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS /* - * fsnotify_file_area_perm - permission hook before access to file range + * fsnotify_file_area_perm - permission hook before access/modify of file range */ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, const loff_t *ppos, size_t count) { - __u32 fsnotify_mask = FS_ACCESS_PERM; + struct inode *inode = file_inode(file); + __u32 fsnotify_mask; /* * filesystem may be modified in the context of permission events @@ -147,7 +148,27 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, */ lockdep_assert_once(file_write_not_started(file)); - if (!(perm_mask & MAY_READ)) + /* + * Generate FS_PRE_ACCESS/FS_ACCESS_PERM as two seperate events. + */ + if (perm_mask & MAY_READ) { + int ret = fsnotify_file(file, FS_ACCESS_PERM); + + if (ret) + return ret; + } + + /* + * Pre-content events are only reported for regular files and dirs. + */ + if (!S_ISDIR(inode->i_mode) && !S_ISREG(inode->i_mode)) + return 0; + + if (perm_mask & MAY_WRITE) + fsnotify_mask = FS_PRE_MODIFY; + else if (perm_mask & MAY_READ) + fsnotify_mask = FS_PRE_ACCESS; + else return 0; return fsnotify_file(file, fsnotify_mask); diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index 8be029bc50b1..21e72b837ec5 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -56,6 +56,9 @@ #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */ #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */ +#define FS_PRE_ACCESS 0x00100000 /* Pre-content access hook */ +#define FS_PRE_MODIFY 0x00200000 /* Pre-content modify hook */ + /* * Set on inode mark that cares about things that happen to its children. * Always set for dnotify and inotify. @@ -77,8 +80,14 @@ */ #define ALL_FSNOTIFY_DIRENT_EVENTS (FS_CREATE | FS_DELETE | FS_MOVE | FS_RENAME) -#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \ - FS_OPEN_EXEC_PERM) +/* Content events can be used to inspect file content */ +#define FSNOTIFY_CONTENT_PERM_EVENTS (FS_OPEN_PERM | FS_OPEN_EXEC_PERM | \ + FS_ACCESS_PERM) +/* Pre-content events can be used to fill file content */ +#define FSNOTIFY_PRE_CONTENT_EVENTS (FS_PRE_ACCESS | FS_PRE_MODIFY) + +#define ALL_FSNOTIFY_PERM_EVENTS (FSNOTIFY_CONTENT_PERM_EVENTS | \ + FSNOTIFY_PRE_CONTENT_EVENTS) /* * This is a list of all events that may get sent to a parent that is watching diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 55c78c318ccd..2997edf3e7cd 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3406,7 +3406,8 @@ static int selinux_path_notify(const struct path *path, u64 mask, perm |= FILE__WATCH_WITH_PERM; /* watches on read-like events need the file:watch_reads permission */ - if (mask & (FS_ACCESS | FS_ACCESS_PERM | FS_CLOSE_NOWRITE)) + if (mask & (FS_ACCESS | FS_ACCESS_PERM | FS_PRE_ACCESS | + FS_CLOSE_NOWRITE)) perm |= FILE__WATCH_READS; return path_has_perm(current_cred(), path, perm);