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| author | Christophe Leroy <christophe.leroy@csgroup.eu> | 2021-02-01 07:29:50 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-03-01 02:33:31 +0100 |
| commit | c119565a15a628efdfa51352f9f6c5186e506a1c (patch) | |
| tree | dd66c71355989680c652ae52cbe150b588b23fb6 /arch/powerpc/kernel/head_book3s_32.S | |
| parent | powerpc/pseries: Don't enforce MSI affinity with kdump (diff) | |
| download | linux-c119565a15a628efdfa51352f9f6c5186e506a1c.tar.xz linux-c119565a15a628efdfa51352f9f6c5186e506a1c.zip | |
powerpc/603: Fix protection of user pages mapped with PROT_NONE
On book3s/32, page protection is defined by the PP bits in the PTE
which provide the following protection depending on the access
keys defined in the matching segment register:
- PP 00 means RW with key 0 and N/A with key 1.
- PP 01 means RW with key 0 and RO with key 1.
- PP 10 means RW with both key 0 and key 1.
- PP 11 means RO with both key 0 and key 1.
Since the implementation of kernel userspace access protection,
PP bits have been set as follows:
- PP00 for pages without _PAGE_USER
- PP01 for pages with _PAGE_USER and _PAGE_RW
- PP11 for pages with _PAGE_USER and without _PAGE_RW
For kernelspace segments, kernel accesses are performed with key 0
and user accesses are performed with key 1. As PP00 is used for
non _PAGE_USER pages, user can't access kernel pages not flagged
_PAGE_USER while kernel can.
For userspace segments, both kernel and user accesses are performed
with key 0, therefore pages not flagged _PAGE_USER are still
accessible to the user.
This shouldn't be an issue, because userspace is expected to be
accessible to the user. But unlike most other architectures, powerpc
implements PROT_NONE protection by removing _PAGE_USER flag instead of
flagging the page as not valid. This means that pages in userspace
that are not flagged _PAGE_USER shall remain inaccessible.
To get the expected behaviour, just mimic other architectures in the
TLB miss handler by checking _PAGE_USER permission on userspace
accesses as if it was the _PAGE_PRESENT bit.
Note that this problem only is only for 603 cores. The 604+ have
an hash table, and hash_page() function already implement the
verification of _PAGE_USER permission on userspace pages.
Fixes: f342adca3afc ("powerpc/32s: Prepare Kernel Userspace Access Protection")
Cc: stable@vger.kernel.org # v5.2+
Reported-by: Christoph Plattner <christoph.plattner@thalesgroup.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4a0c6e3bb8f0c162457bf54d9bc6fd8d7b55129f.1612160907.git.christophe.leroy@csgroup.eu
Diffstat (limited to 'arch/powerpc/kernel/head_book3s_32.S')
| -rw-r--r-- | arch/powerpc/kernel/head_book3s_32.S | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S index 727fdab557c9..565e84e20a72 100644 --- a/arch/powerpc/kernel/head_book3s_32.S +++ b/arch/powerpc/kernel/head_book3s_32.S @@ -457,11 +457,12 @@ InstructionTLBMiss: cmplw 0,r1,r3 #endif mfspr r2, SPRN_SDR1 - li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC + li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC | _PAGE_USER rlwinm r2, r2, 28, 0xfffff000 #ifdef CONFIG_MODULES bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_EXEC addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ #endif 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ @@ -520,10 +521,11 @@ DataLoadTLBMiss: lis r1, TASK_SIZE@h /* check if kernel address */ cmplw 0,r1,r3 mfspr r2, SPRN_SDR1 - li r1, _PAGE_PRESENT | _PAGE_ACCESSED + li r1, _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER rlwinm r2, r2, 28, 0xfffff000 bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1, _PAGE_PRESENT | _PAGE_ACCESSED addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ lwz r2,0(r2) /* get pmd entry */ @@ -597,10 +599,11 @@ DataStoreTLBMiss: lis r1, TASK_SIZE@h /* check if kernel address */ cmplw 0,r1,r3 mfspr r2, SPRN_SDR1 - li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER rlwinm r2, r2, 28, 0xfffff000 bgt- 112f lis r2, (swapper_pg_dir - PAGE_OFFSET)@ha /* if kernel address, use */ + li r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED addi r2, r2, (swapper_pg_dir - PAGE_OFFSET)@l /* kernel page table */ 112: rlwimi r2,r3,12,20,29 /* insert top 10 bits of address */ lwz r2,0(r2) /* get pmd entry */ |