| Message ID | 20210203020755.117593-1-aik@ozlabs.ru (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [kernel,v2] powerpc/uaccess: Skip might_fault() when user access is enabled | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (44158b256b30415079588d0fcb1bccbdc2ccd009) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 501c9a79038c..27e109866c42 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -313,7 +313,7 @@ do { \ __typeof__(size) __gu_size = (size); \ \ __chk_user_ptr(__gu_addr); \ - if (!is_kernel_addr((unsigned long)__gu_addr)) \ + if (do_allow && !is_kernel_addr((unsigned long)__gu_addr)) \ might_fault(); \ barrier_nospec(); \ if (do_allow) \
The amount of code executed with enabled user space access (unlocked KUAP) should be minimal. However with CONFIG_PROVE_LOCKING or CONFIG_DEBUG_ATOMIC_SLEEP enabled, might_fault() may end up replaying interrupts which in turn may access the user space and forget to restore the KUAP state. The problem places are strncpy_from_user (and similar) which unlock KUAP and call unsafe_get_user -> __get_user_allowed -> __get_user_nocheck() with do_allow=false to skip KUAP as the caller took care of it. This changes __get_user_nocheck() to look at @do_allow to decide whether to skip might_fault(). Since strncpy_from_user/etc call might_fault() anyway before unlocking KUAP, there should be no visible change. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- Changes: v2: * s/!do_allow/do_allow/ --- arch/powerpc/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)