On 08/01/2024 11:23, Amit Daniel Kachhap wrote:
The existing userspace may not use the maximum protection bits in the protection flags introduced by PCuABI and hence such applications may have inconsistency in the memory protection flag updated via mprotect() syscall with the capability permission bits.
Reduce the impact of such failures by setting the capability to maximum permission if no maximum protection bits are detected.
We do want to detect applications that require PROT_MAX() but do not use it. These should be rare cases (e.g. a JIT that creates an RW mapping initially and then makes it RX, in which case PROT_MAX(RWX) is required). With this patch, tests that expect PCuABI to be implemented as specified should fail.
Kevin
Signed-off-by: Amit Daniel Kachhap amitdaniel.kachhap@arm.com
mm/cap_addr_mgmt.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/mm/cap_addr_mgmt.c b/mm/cap_addr_mgmt.c index 5ff4fdf26d28..68139abd004a 100644 --- a/mm/cap_addr_mgmt.c +++ b/mm/cap_addr_mgmt.c @@ -228,6 +228,12 @@ cheri_perms_t mapping_to_capability_perm(int prot, bool has_tag_access) { cheri_perms_t perms = 0;
- if (!PROT_MAX_EXTRACT(prot)) {
perms = CHERI_PERMS_READ | CHERI_PERMS_WRITE |CHERI_PERMS_EXEC | CHERI_PERMS_ROOTCAP;goto skip_calc_perm;- }
- if (mapping_may_have_prot_flag(prot, PROT_READ)) { perms |= CHERI_PERM_LOAD; if (has_tag_access)
@@ -247,6 +253,7 @@ cheri_perms_t mapping_to_capability_perm(int prot, bool has_tag_access) perms |= arch_map_to_cap_perm(PROT_MAX_EXTRACT(prot) ? PROT_MAX_EXTRACT(prot) : prot, has_tag_access); perms |= CHERI_PERMS_ROOTCAP; +skip_calc_perm: return perms; }