| Message ID | 20231201094636.19770-4-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm, security, bpf: Fine-grained control over memory policy adjustments with lsm bpf | expand |
On Fri, Dec 01, 2023 at 09:46:32AM +0000, Yafang Shao wrote: > Considering that MPOL_F_NUMA_BALANCING or mbind(2) using either > MPOL_MF_MOVE or MPOL_MF_MOVE_ALL are capable of memory movement, it's > essential to include security_task_movememory() to cover this > functionality as well. It was identified during a code review. Hm - this doesn't have any bad side effects for you when using selinux? The selinux_task_movememory() hook checks for PROCESS__SETSCHED privs. The two existing security_task_movememory() calls are in cases where we expect the caller to be affecting another task identified by pid, so that makes sense. Is an MPOL_MV_MOVE to move your own pages actually analogous to that? Much like the concern you mentioned in your intro about requiring CAP_SYS_NICE and thereby expanding its use, it seems that here you will be regressing some mbind users unless the granting of PROCESS__SETSCHED is widened. > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > --- > mm/mempolicy.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 10a590ee1c89..1eafe81d782e 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1259,8 +1259,15 @@ static long do_mbind(unsigned long start, unsigned long len, > if (!new) > flags |= MPOL_MF_DISCONTIG_OK; > > - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) > + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) { MPOL_MF_MOVE_ALL already has a CAP_SYS_NICE check. Does that suffice for that one? > + err = security_task_movememory(current); > + if (err) { > + mpol_put(new); > + return err; > + } > lru_cache_disable(); > + } > + > { > NODEMASK_SCRATCH(scratch); > if (scratch) { > @@ -1450,6 +1457,8 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode, > /* Basic parameter sanity check used by both mbind() and set_mempolicy() */ > static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) > { > + int err; > + > *flags = *mode & MPOL_MODE_FLAGS; > *mode &= ~MPOL_MODE_FLAGS; > > @@ -1460,6 +1469,9 @@ static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) > if (*flags & MPOL_F_NUMA_BALANCING) { > if (*mode != MPOL_BIND) > return -EINVAL; > + err = security_task_movememory(current); > + if (err) > + return err; > *flags |= (MPOL_F_MOF | MPOL_F_MORON); > } > return 0; > -- > 2.30.1 (Apple Git-130)
On Sat, Dec 2, 2023 at 4:50 AM Serge E. Hallyn <serge@hallyn.com> wrote: > > On Fri, Dec 01, 2023 at 09:46:32AM +0000, Yafang Shao wrote: > > Considering that MPOL_F_NUMA_BALANCING or mbind(2) using either > > MPOL_MF_MOVE or MPOL_MF_MOVE_ALL are capable of memory movement, it's > > essential to include security_task_movememory() to cover this > > functionality as well. It was identified during a code review. > > Hm - this doesn't have any bad side effects for you when using selinux? > The selinux_task_movememory() hook checks for PROCESS__SETSCHED privs. > The two existing security_task_movememory() calls are in cases where we > expect the caller to be affecting another task identified by pid, so > that makes sense. Is an MPOL_MV_MOVE to move your own pages actually > analogous to that? > > Much like the concern you mentioned in your intro about requiring > CAP_SYS_NICE and thereby expanding its use, it seems that here you > will be regressing some mbind users unless the granting of PROCESS__SETSCHED > is widened. Ah, it appears that this change might lead to regression. I overlooked its association with the PROCESS__SETSCHED privilege. I'll exclude this patch from the upcoming version. Thanks for your review.
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 10a590ee1c89..1eafe81d782e 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1259,8 +1259,15 @@ static long do_mbind(unsigned long start, unsigned long len, if (!new) flags |= MPOL_MF_DISCONTIG_OK; - if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) { + err = security_task_movememory(current); + if (err) { + mpol_put(new); + return err; + } lru_cache_disable(); + } + { NODEMASK_SCRATCH(scratch); if (scratch) { @@ -1450,6 +1457,8 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode, /* Basic parameter sanity check used by both mbind() and set_mempolicy() */ static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) { + int err; + *flags = *mode & MPOL_MODE_FLAGS; *mode &= ~MPOL_MODE_FLAGS; @@ -1460,6 +1469,9 @@ static inline int sanitize_mpol_flags(int *mode, unsigned short *flags) if (*flags & MPOL_F_NUMA_BALANCING) { if (*mode != MPOL_BIND) return -EINVAL; + err = security_task_movememory(current); + if (err) + return err; *flags |= (MPOL_F_MOF | MPOL_F_MORON); } return 0;
Considering that MPOL_F_NUMA_BALANCING or mbind(2) using either MPOL_MF_MOVE or MPOL_MF_MOVE_ALL are capable of memory movement, it's essential to include security_task_movememory() to cover this functionality as well. It was identified during a code review. Signed-off-by: Yafang Shao <laoar.shao@gmail.com> --- mm/mempolicy.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)