6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: John David Anglin dave.anglin@bell.net
commit f6334f4ae9a4e962ba74b026e1d965dfdf8cbef8 upstream.
We use load and stbys,e instructions to trigger memory reference interruptions without writing to memory. Because of the way read access support is implemented, read access interruptions are only triggered at privilege levels 2 and 3. The kernel and gateway page execute at privilege level 0, so this code never triggers a read access interruption. Thus, it is currently possible for user code to execute a LWS compare and swap operation at an address that is read protected at privilege level 3 (PRIV_USER).
Fix this by probing read access rights at privilege level 3 and branching to lws_fault if access isn't allowed.
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/kernel/syscall.S | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-)
--- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -613,6 +613,9 @@ lws_compare_and_swap32: lws_compare_and_swap: /* Trigger memory reference interruptions without writing to memory */ 1: ldw 0(%r26), %r28 + proberi (%r26), PRIV_USER, %r28 + comb,=,n %r28, %r0, lws_fault /* backwards, likely not taken */ + nop 2: stbys,e %r0, 0(%r26)
/* Calculate 8-bit hash index from virtual address */ @@ -767,6 +770,9 @@ cas2_lock_start: copy %r26, %r28 depi_safe 0, 31, 2, %r28 10: ldw 0(%r28), %r1 + proberi (%r28), PRIV_USER, %r1 + comb,=,n %r1, %r0, lws_fault /* backwards, likely not taken */ + nop 11: stbys,e %r0, 0(%r28)
/* Calculate 8-bit hash index from virtual address */ @@ -951,41 +957,47 @@ atomic_xchg_begin:
/* 8-bit exchange */ 1: ldb 0(%r24), %r20 + proberi (%r24), PRIV_USER, %r20 + comb,=,n %r20, %r0, lws_fault /* backwards, likely not taken */ + nop copy %r23, %r20 depi_safe 0, 31, 2, %r20 b atomic_xchg_start 2: stbys,e %r0, 0(%r20) - nop - nop - nop
/* 16-bit exchange */ 3: ldh 0(%r24), %r20 + proberi (%r24), PRIV_USER, %r20 + comb,=,n %r20, %r0, lws_fault /* backwards, likely not taken */ + nop copy %r23, %r20 depi_safe 0, 31, 2, %r20 b atomic_xchg_start 4: stbys,e %r0, 0(%r20) - nop - nop - nop
/* 32-bit exchange */ 5: ldw 0(%r24), %r20 + proberi (%r24), PRIV_USER, %r20 + comb,=,n %r20, %r0, lws_fault /* backwards, likely not taken */ + nop b atomic_xchg_start 6: stbys,e %r0, 0(%r23) nop nop - nop - nop - nop
/* 64-bit exchange */ #ifdef CONFIG_64BIT 7: ldd 0(%r24), %r20 + proberi (%r24), PRIV_USER, %r20 + comb,=,n %r20, %r0, lws_fault /* backwards, likely not taken */ + nop 8: stdby,e %r0, 0(%r23) #else 7: ldw 0(%r24), %r20 8: ldw 4(%r24), %r20 + proberi (%r24), PRIV_USER, %r20 + comb,=,n %r20, %r0, lws_fault /* backwards, likely not taken */ + nop copy %r23, %r20 depi_safe 0, 31, 2, %r20 9: stbys,e %r0, 0(%r20)