[PATCH AUTOSEL 5.4 2/3] powerpc/pseries: Enforce hcall result buffer validity and size

[PATCH AUTOSEL 5.4 2/3] powerpc/pseries: Enforce hcall result buffer validity and size

[Sasha Levin]

From: Nathan Lynch <nathanl@linux.ibm.com>

[ Upstream commit ff2e185cf73df480ec69675936c4ee75a445c3e4 ]

plpar_hcall(), plpar_hcall9(), and related functions expect callers to
provide valid result buffers of certain minimum size. Currently this
is communicated only through comments in the code and the compiler has
no idea.

For example, if I write a bug like this:

  long retbuf[PLPAR_HCALL_BUFSIZE]; // should be PLPAR_HCALL9_BUFSIZE
  plpar_hcall9(H_ALLOCATE_VAS_WINDOW, retbuf, ...);

This compiles with no diagnostics emitted, but likely results in stack
corruption at runtime when plpar_hcall9() stores results past the end
of the array. (To be clear this is a contrived example and I have not
found a real instance yet.)

To make this class of error less likely, we can use explicitly-sized
array parameters instead of pointers in the declarations for the hcall
APIs. When compiled with -Warray-bounds[1], the code above now
provokes a diagnostic like this:

error: array argument is too small;
is of size 32, callee requires at least 72 [-Werror,-Warray-bounds]
   60 |                 plpar_hcall9(H_ALLOCATE_VAS_WINDOW, retbuf,
      |                 ^                                   ~~~~~~

[1] Enabled for LLVM builds but not GCC for now. See commit
    0da6e5fd6c37 ("gcc: disable '-Warray-bounds' for gcc-13 too") and
    related changes.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240408-pseries-hvcall-retbuf-v1-1-ebc73d7253cf@linux.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/include/asm/hvcall.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 11112023e327d..344330b17376f 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -403,7 +403,7 @@ long plpar_hcall_norets(unsigned long opcode, ...);
  * Used for all but the craziest of phyp interfaces (see plpar_hcall9)
  */
 #define PLPAR_HCALL_BUFSIZE 4
-long plpar_hcall(unsigned long opcode, unsigned long *retbuf, ...);
+long plpar_hcall(unsigned long opcode, unsigned long retbuf[static PLPAR_HCALL_BUFSIZE], ...);
 
 /**
  * plpar_hcall_raw: - Make a hypervisor call without calculating hcall stats
@@ -417,7 +417,7 @@ long plpar_hcall(unsigned long opcode, unsigned long *retbuf, ...);
  * plpar_hcall, but plpar_hcall_raw works in real mode and does not
  * calculate hypervisor call statistics.
  */
-long plpar_hcall_raw(unsigned long opcode, unsigned long *retbuf, ...);
+long plpar_hcall_raw(unsigned long opcode, unsigned long retbuf[static PLPAR_HCALL_BUFSIZE], ...);
 
 /**
  * plpar_hcall9: - Make a pseries hypervisor call with up to 9 return arguments
@@ -428,8 +428,8 @@ long plpar_hcall_raw(unsigned long opcode, unsigned long *retbuf, ...);
  * PLPAR_HCALL9_BUFSIZE to size the return argument buffer.
  */
 #define PLPAR_HCALL9_BUFSIZE 9
-long plpar_hcall9(unsigned long opcode, unsigned long *retbuf, ...);
-long plpar_hcall9_raw(unsigned long opcode, unsigned long *retbuf, ...);
+long plpar_hcall9(unsigned long opcode, unsigned long retbuf[static PLPAR_HCALL9_BUFSIZE], ...);
+long plpar_hcall9_raw(unsigned long opcode, unsigned long retbuf[static PLPAR_HCALL9_BUFSIZE], ...);
 
 struct hvcall_mpp_data {
 	unsigned long entitled_mem;
-- 
2.43.0

[PATCH AUTOSEL 5.4 3/3] powerpc/io: Avoid clang null pointer arithmetic warnings

[Sasha Levin]

From: Michael Ellerman <mpe@ellerman.id.au>

[ Upstream commit 03c0f2c2b2220fc9cf8785cd7b61d3e71e24a366 ]

With -Wextra clang warns about pointer arithmetic using a null pointer.
When building with CONFIG_PCI=n, that triggers a warning in the IO
accessors, eg:

  In file included from linux/arch/powerpc/include/asm/io.h:672:
  linux/arch/powerpc/include/asm/io-defs.h:23:1: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     23 | DEF_PCI_AC_RET(inb, u8, (unsigned long port), (port), pio, port)
        | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ...
  linux/arch/powerpc/include/asm/io.h:591:53: note: expanded from macro '__do_inb'
    591 | #define __do_inb(port)          readb((PCI_IO_ADDR)_IO_BASE + port);
        |                                       ~~~~~~~~~~~~~~~~~~~~~ ^

That is because when CONFIG_PCI=n, _IO_BASE is defined as 0.

Although _IO_BASE is defined as plain 0, the cast (PCI_IO_ADDR) converts
it to void * before the addition with port happens.

Instead the addition can be done first, and then the cast. The resulting
value will be the same, but avoids the warning, and also avoids void
pointer arithmetic which is apparently non-standard.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Closes: https://lore.kernel.org/all/CA+G9fYtEh8zmq8k8wE-8RZwW-Qr927RLTn+KqGnq1F=ptaaNsA@mail.gmail.com
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240503075619.394467-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/include/asm/io.h | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index daba2d2a02a0b..e86516ff8f4b3 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -542,12 +542,12 @@ __do_out_asm(_rec_outl, "stwbrx")
 #define __do_inw(port)		_rec_inw(port)
 #define __do_inl(port)		_rec_inl(port)
 #else /* CONFIG_PPC32 */
-#define __do_outb(val, port)	writeb(val,(PCI_IO_ADDR)_IO_BASE+port);
-#define __do_outw(val, port)	writew(val,(PCI_IO_ADDR)_IO_BASE+port);
-#define __do_outl(val, port)	writel(val,(PCI_IO_ADDR)_IO_BASE+port);
-#define __do_inb(port)		readb((PCI_IO_ADDR)_IO_BASE + port);
-#define __do_inw(port)		readw((PCI_IO_ADDR)_IO_BASE + port);
-#define __do_inl(port)		readl((PCI_IO_ADDR)_IO_BASE + port);
+#define __do_outb(val, port)	writeb(val,(PCI_IO_ADDR)(_IO_BASE+port));
+#define __do_outw(val, port)	writew(val,(PCI_IO_ADDR)(_IO_BASE+port));
+#define __do_outl(val, port)	writel(val,(PCI_IO_ADDR)(_IO_BASE+port));
+#define __do_inb(port)		readb((PCI_IO_ADDR)(_IO_BASE + port));
+#define __do_inw(port)		readw((PCI_IO_ADDR)(_IO_BASE + port));
+#define __do_inl(port)		readl((PCI_IO_ADDR)(_IO_BASE + port));
 #endif /* !CONFIG_PPC32 */
 
 #ifdef CONFIG_EEH
@@ -563,12 +563,12 @@ __do_out_asm(_rec_outl, "stwbrx")
 #define __do_writesw(a, b, n)	_outsw(PCI_FIX_ADDR(a),(b),(n))
 #define __do_writesl(a, b, n)	_outsl(PCI_FIX_ADDR(a),(b),(n))
 
-#define __do_insb(p, b, n)	readsb((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
-#define __do_insw(p, b, n)	readsw((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
-#define __do_insl(p, b, n)	readsl((PCI_IO_ADDR)_IO_BASE+(p), (b), (n))
-#define __do_outsb(p, b, n)	writesb((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
-#define __do_outsw(p, b, n)	writesw((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
-#define __do_outsl(p, b, n)	writesl((PCI_IO_ADDR)_IO_BASE+(p),(b),(n))
+#define __do_insb(p, b, n)	readsb((PCI_IO_ADDR)(_IO_BASE+(p)), (b), (n))
+#define __do_insw(p, b, n)	readsw((PCI_IO_ADDR)(_IO_BASE+(p)), (b), (n))
+#define __do_insl(p, b, n)	readsl((PCI_IO_ADDR)(_IO_BASE+(p)), (b), (n))
+#define __do_outsb(p, b, n)	writesb((PCI_IO_ADDR)(_IO_BASE+(p)),(b),(n))
+#define __do_outsw(p, b, n)	writesw((PCI_IO_ADDR)(_IO_BASE+(p)),(b),(n))
+#define __do_outsl(p, b, n)	writesl((PCI_IO_ADDR)(_IO_BASE+(p)),(b),(n))
 
 #define __do_memset_io(addr, c, n)	\
 				_memset_io(PCI_FIX_ADDR(addr), c, n)
-- 
2.43.0