@@ -131,12 +131,17 @@ static inline void prevent_user_access(void __user *to, const void __user *from,
kuap_update_sr(mfsrin(addr) | SR_KS, addr, end); /* set Ks */
}
-static inline bool bad_kuap_fault(struct pt_regs *regs, bool is_write)
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
+ unsigned long begin = regs->kuap & 0xf0000000;
+ unsigned long end = regs->kuap << 28;
+
if (!is_write)
return false;
- return WARN(!regs->kuap, "Bug: write fault blocked by segment registers !");
+ return WARN(address < begin || address >= end,
+ "Bug: write fault blocked by segment registers !");
}
#endif /* CONFIG_PPC_KUAP */
@@ -95,7 +95,8 @@ static inline void prevent_user_access(void __user *to, const void __user *from,
set_kuap(AMR_KUAP_BLOCKED);
}
-static inline bool bad_kuap_fault(struct pt_regs *regs, bool is_write)
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
return WARN(mmu_has_feature(MMU_FTR_RADIX_KUAP) &&
(regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
@@ -45,7 +45,11 @@ static inline void allow_user_access(void __user *to, const void __user *from,
unsigned long size) { }
static inline void prevent_user_access(void __user *to, const void __user *from,
unsigned long size) { }
-static inline bool bad_kuap_fault(struct pt_regs *regs, bool is_write) { return false; }
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
+{
+ return false;
+}
#endif /* CONFIG_PPC_KUAP */
static inline void allow_read_from_user(const void __user *from, unsigned long size)
@@ -46,7 +46,8 @@ static inline void prevent_user_access(void __user *to, const void __user *from,
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
-static inline bool bad_kuap_fault(struct pt_regs *regs, bool is_write)
+static inline bool
+bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xf0000000),
"Bug: fault blocked by AP register !");
@@ -233,7 +233,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
// Read/write fault in a valid region (the exception table search passed
// above), but blocked by KUAP is bad, it can never succeed.
- if (bad_kuap_fault(regs, is_write))
+ if (bad_kuap_fault(regs, address, is_write))
return true;
// What's left? Kernel fault on user in well defined regions (extable
At the moment, bad_kuap_fault() reports a fault only if a bad access to userspace occurred while access to userspace was not granted. But if a fault occurs for a write outside the allowed userspace segment(s) that have been unlocked, bad_kuap_fault() fails to detect it and the kernel loops forever in do_page_fault(). Fix it by checking that the accessed address is within the allowed range. Fixes: a68c31fc01ef ("powerpc/32s: Implement Kernel Userspace Access Protection") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1e07c7de4ffdd9cda35d1ffe8258af75579d3e91.1579715466.git.christophe.leroy@c-s.fr --- v4: taken from powerpc/next-test --- arch/powerpc/include/asm/book3s/32/kup.h | 9 +++++++-- arch/powerpc/include/asm/book3s/64/kup-radix.h | 3 ++- arch/powerpc/include/asm/kup.h | 6 +++++- arch/powerpc/include/asm/nohash/32/kup-8xx.h | 3 ++- arch/powerpc/mm/fault.c | 2 +- 5 files changed, 17 insertions(+), 6 deletions(-)