6.1-stable review patch. If anyone has any objections, please let me know.
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From: John David Anglin dave.anglin@bell.net
commit 89f686a0fb6e473a876a9a60a13aec67a62b9a7e upstream.
Because of the way read access support is implemented, read access interruptions are only triggered at privilege levels 2 and 3. The kernel executes at privilege level 0, so __get_user() never triggers a read access interruption (code 26). Thus, it is currently possible for user code to access a read protected address via a system call.
Fix this by probing read access rights at privilege level 3 (PRIV_USER) and setting __gu_err to -EFAULT (-14) if access isn't allowed.
Note the cmpiclr instruction does a 32-bit compare because COND macro doesn't work inside asm.
Signed-off-by: John David Anglin dave.anglin@bell.net Signed-off-by: Helge Deller deller@gmx.de Cc: stable@vger.kernel.org # v5.12+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/parisc/include/asm/uaccess.h | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
--- a/arch/parisc/include/asm/uaccess.h +++ b/arch/parisc/include/asm/uaccess.h @@ -42,9 +42,24 @@ __gu_err; \ })
-#define __get_user(val, ptr) \ -({ \ - __get_user_internal(SR_USER, val, ptr); \ +#define __probe_user_internal(sr, error, ptr) \ +({ \ + __asm__("\tproberi (%%sr%1,%2),%3,%0\n" \ + "\tcmpiclr,= 1,%0,%0\n" \ + "\tldi %4,%0\n" \ + : "=r"(error) \ + : "i"(sr), "r"(ptr), "i"(PRIV_USER), \ + "i"(-EFAULT)); \ +}) + +#define __get_user(val, ptr) \ +({ \ + register long __gu_err; \ + \ + __gu_err = __get_user_internal(SR_USER, val, ptr); \ + if (likely(!__gu_err)) \ + __probe_user_internal(SR_USER, __gu_err, ptr); \ + __gu_err; \ })
#define __get_user_asm(sr, val, ldx, ptr) \