In certain cases a xml contains paths that do not yet exist, but are valid as qemu will create them later on - for example vhostuser mode=server sockets. In any such cases so far the check to virFileExists failed and due to that the paths stayed non-resolved in regard to symlinks. But for apparmor those non-resolved rules are non functional as they are evaluated after resolving any symlinks. Therefore for non-existent files and partially non-existent paths resolve as much as possible to get valid rules. Example: <interface type='vhostuser'> <model type='virtio'/> <source type='unix' path='/var/run/symlinknet' mode='server'/> </interface> Got rendered as: "/var/run/symlinknet" rw, But correct with "/var/run" being a symlink to "/run" is: "/run/symlinknet" rw, Signed-off-by: Christian Ehrhardt <christian.ehrhardt(a)canonical.com&gt; --- src/security/virt-aa-helper.c | 45 ++++++++++++++++++++++++++++++ ++++++------- 1 file changed, 38 insertions(+), 7 deletions(-) diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c index ff0068c..91bc339 100644 --- a/src/security/virt-aa-helper.c +++ b/src/security/virt-aa-helper.c @@ -41,6 +41,7 @@ #include "viralloc.h" #include "vircommand.h" #include "virlog.h" +#include "dirname.h" #include "driver.h" #include "security_driver.h" @@ -752,6 +753,9 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi bool explicit_deny_rule = true; char *sub = NULL; char *perms_new = NULL; + char *pathdir = NULL; + char *pathtmp = NULL; + char *pathreal = NULL; if (path == NULL) return rc; @@ -766,14 +770,38 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi return 0; } - if (virFileExists(path)) { - if ((tmp = realpath(path, NULL)) == NULL) { - vah_error(NULL, 0, path); - vah_error(NULL, 0, _("could not find realpath for disk")); - return rc; + /* files might be created by qemu later on and not exist right now. + * But realpath needs a valid path to work on, therefore: + * 1. walk the path to find longest valid path + * 2. get the realpath of that valid path + * 3. re-combine the realpath with the remaining suffix + * Note: A totally non existent path is used as-is + */ + if ((pathdir = mdir_name(path)) == NULL) + goto cleanup; + while (!virFileExists(pathdir)) { + if (VIR_STRDUP_QUIET(pathtmp, pathdir) < 0) + goto cleanup; + VIR_FREE(pathdir); + if ((pathdir = mdir_name(pathtmp)) == NULL) + goto cleanup; + VIR_FREE(pathtmp); + } + + if (strlen(pathdir) == 1) { + /* nothing of the path does exist yet */ + if (VIR_STRDUP_QUIET(tmp, path) < 0) + goto cleanup; + } else { + if (VIR_STRDUP_QUIET(pathtmp, path+strlen(pathdir)) < 0) + goto cleanup; + if ((pathreal = realpath(pathdir, NULL)) == NULL) { + vah_error(NULL, 0, pathdir); + vah_error(NULL, 0, _("could not find realpath")); + goto cleanup; } - } else if (VIR_STRDUP_QUIET(tmp, path) < 0) { - return rc; + if (virAsprintfQuiet(&tmp, "%s%s", pathreal, pathtmp) < 0) + goto cleanup; } if (VIR_STRDUP_QUIET(perms_new, perms) < 0) @@ -814,6 +842,9 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi } cleanup: + VIR_FREE(pathdir); + VIR_FREE(pathtmp); + VIR_FREE(pathreal); VIR_FREE(perms_new); VIR_FREE(tmp); -- 2.7.4

On 03/01/2018 03:53 PM, Christian Ehrhardt wrote: > In certain cases a xml contains paths that do not yet exist, but > are valid as qemu will create them later on - for example > vhostuser mode=server sockets. > > In any such cases so far the check to virFileExists failed and due to > that the paths stayed non-resolved in regard to symlinks. > > But for apparmor those non-resolved rules are non functional as they > are evaluated after resolving any symlinks. > > Therefore for non-existent files and partially non-existent paths > resolve as much as possible to get valid rules. > > Example: > <interface type='vhostuser'> > <model type='virtio'/> > <source type='unix' > path='/var/run/symlinknet' > mode='server'/> Don't be afraid to write this on one line. Firstly, the 80 character line is just a soft limit, secondly I like to see verbatim text unchanged. But feel free to keep it as it is. Your call. > </interface> > > Got rendered as: > "/var/run/symlinknet" rw, > > But correct with "/var/run" being a symlink to "/run" is: > "/run/symlinknet" rw, > > Signed-off-by: Christian Ehrhardt <christian.ehrhardt(a)canonical.com&gt; > --- > src/security/virt-aa-helper.c | 45 ++++++++++++++++++++++++++++++ ++++++------- > 1 file changed, 38 insertions(+), 7 deletions(-) > > diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c > index ff0068c..91bc339 100644 > --- a/src/security/virt-aa-helper.c > +++ b/src/security/virt-aa-helper.c > @@ -41,6 +41,7 @@ > #include "viralloc.h" > #include "vircommand.h" > #include "virlog.h" > +#include "dirname.h" > #include "driver.h" > > #include "security_driver.h" > @@ -752,6 +753,9 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi > bool explicit_deny_rule = true; > char *sub = NULL; > char *perms_new = NULL; > + char *pathdir = NULL; > + char *pathtmp = NULL; > + char *pathreal = NULL; > > if (path == NULL) > return rc; > @@ -766,14 +770,38 @@ vah_add_path(virBufferPtr buf, const char *path, const char *perms, bool recursi > return 0; > } > > - if (virFileExists(path)) { > - if ((tmp = realpath(path, NULL)) == NULL) { > - vah_error(NULL, 0, path); > - vah_error(NULL, 0, _("could not find realpath for disk")); > - return rc; > + /* files might be created by qemu later on and not exist right now. > + * But realpath needs a valid path to work on, therefore: > + * 1. walk the path to find longest valid path > + * 2. get the realpath of that valid path > + * 3. re-combine the realpath with the remaining suffix > + * Note: A totally non existent path is used as-is > + */ > + if ((pathdir = mdir_name(path)) == NULL) > + goto cleanup; > + while (!virFileExists(pathdir)) { > + if (VIR_STRDUP_QUIET(pathtmp, pathdir) < 0) > + goto cleanup; > + VIR_FREE(pathdir); > + if ((pathdir = mdir_name(pathtmp)) == NULL) > + goto cleanup; > + VIR_FREE(pathtmp); > + } I guess this can be written simpler: if ((pathdir = mdir_name(path)) == NULL) goto cleanup; while (!virFileExists(pathdir)) { if ((pathtmp = mdir_name(pathdir)) == NULL) goto cleanup; VIR_FREE(pathdir); VIR_STEAL_PTR(pathdir, pathtmp); } ACK whether you decide to go with my way (untested though) or what you have. Sorry for the delay.

Michal