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0c389d89ab
Now that we've renamed probe_kernel_address() to get_kernel_nofault()
and made it look and behave more in line with get_user(), some of the
subtle type behavior differences end up being more obvious and possibly
dangerous.
When you do
get_user(val, user_ptr);
the type of the access comes from the "user_ptr" part, and the above
basically acts as
val = *user_ptr;
by design (except, of course, for the fact that the actual dereference
is done with a user access).
Note how in the above case, the type of the end result comes from the
pointer argument, and then the value is cast to the type of 'val' as
part of the assignment.
So the type of the pointer is ultimately the more important type both
for the access itself.
But 'get_kernel_nofault()' may now _look_ similar, but it behaves very
differently. When you do
get_kernel_nofault(val, kernel_ptr);
it behaves like
val = *(typeof(val) *)kernel_ptr;
except, of course, for the fact that the actual dereference is done with
exception handling so that a faulting access is suppressed and returned
as the error code.
But note how different the casting behavior of the two superficially
similar accesses are: one does the actual access in the size of the type
the pointer points to, while the other does the access in the size of
the target, and ignores the pointer type entirely.
Actually changing get_kernel_nofault() to act like get_user() is almost
certainly the right thing to do eventually, but in the meantime this
patch adds logit to at least verify that the pointer type is compatible
with the type of the result.
In many cases, this involves just casting the pointer to 'void *' to
make it obvious that the type of the pointer is not the important part.
It's not how 'get_user()' acts, but at least the behavioral difference
is now obvious and explicit.
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
52 lines
1.6 KiB
C
52 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_IA64_SECTIONS_H
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#define _ASM_IA64_SECTIONS_H
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/*
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* Copyright (C) 1998-2003 Hewlett-Packard Co
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* David Mosberger-Tang <davidm@hpl.hp.com>
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*/
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#include <linux/elf.h>
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#include <linux/uaccess.h>
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#include <asm-generic/sections.h>
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extern char __phys_per_cpu_start[];
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#ifdef CONFIG_SMP
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extern char __cpu0_per_cpu[];
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#endif
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extern char __start___vtop_patchlist[], __end___vtop_patchlist[];
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extern char __start___rse_patchlist[], __end___rse_patchlist[];
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extern char __start___mckinley_e9_bundles[], __end___mckinley_e9_bundles[];
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extern char __start___phys_stack_reg_patchlist[], __end___phys_stack_reg_patchlist[];
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extern char __start_gate_section[];
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extern char __start_gate_mckinley_e9_patchlist[], __end_gate_mckinley_e9_patchlist[];
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extern char __start_gate_vtop_patchlist[], __end_gate_vtop_patchlist[];
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extern char __start_gate_fsyscall_patchlist[], __end_gate_fsyscall_patchlist[];
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extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_bubble_down_patchlist[];
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extern char __start_unwind[], __end_unwind[];
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extern char __start_ivt_text[], __end_ivt_text[];
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#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
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#undef dereference_function_descriptor
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static inline void *dereference_function_descriptor(void *ptr)
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{
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struct fdesc *desc = ptr;
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void *p;
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if (!get_kernel_nofault(p, (void *)&desc->ip))
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ptr = p;
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return ptr;
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}
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#undef dereference_kernel_function_descriptor
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static inline void *dereference_kernel_function_descriptor(void *ptr)
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{
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if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
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return ptr;
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return dereference_function_descriptor(ptr);
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}
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#endif /* _ASM_IA64_SECTIONS_H */
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