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dtrace: Fix a kernel panic in printm()

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When using printm(), one should always pass a scratch pointer to it.
This is achieved by calling printm with memref

  BEGIN { printm(fixed_len, memref(ptr, var_len)); }

which will return a pointer to the DTrace scratch space of size
sizeof(uintptr_t) * 2. However, one can easily call printm() as follows

  BEGIN { printm(10, (void *)NULL); }

and panic the kernel as a result. This commit does two things:

  (1) adds a new macro DTRACE_INSCRATCHPTR(mstate, ptr, howmany) which
      checks if a certain pointer is in the DTrace scratch space;
  (2) uses DTRACE_INSCRATCHPTR() to implement a check on printm()'s DIFO
      return value in order to avoid the panic and sets CPU_DTRACE_BADADDR
      if the address is not in the scratch space.

Reviewed by:	markj
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D41722
This commit is contained in:
Domagoj Stolfa 2023-09-06 09:25:00 -04:00 committed by Mark Johnston
parent 56e3123fc8
commit 8527bb2aee
1 changed files with 21 additions and 1 deletions
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22
sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
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@ -515,6 +515,11 @@ do { \
((mstate)->dtms_scratch_base + (mstate)->dtms_scratch_size - \
(mstate)->dtms_scratch_ptr >= (alloc_sz))
#define DTRACE_INSCRATCHPTR(mstate, ptr, howmany) \
((ptr) >= (mstate)->dtms_scratch_base && \
(ptr) <= \
((mstate)->dtms_scratch_base + (mstate)->dtms_scratch_size - (howmany)))
#define DTRACE_LOADFUNC(bits) \
/*CSTYLED*/ \
uint##bits##_t \
@ -7739,9 +7744,24 @@ dtrace_probe(dtrace_id_t id, uintptr_t arg0, uintptr_t arg1,
}
case DTRACEACT_PRINTM: {
/* The DIF returns a 'memref'. */
/*
* printm() assumes that the DIF returns a
* pointer returned by memref(). memref() is a
* subroutine that is used to get around the
* single-valued returns of DIF and is assumed
* to always be allocated in the scratch space.
* Therefore, we need to validate that the
* pointer given to printm() is in the scratch
* space in order to avoid a potential panic.
*/
uintptr_t *memref = (uintptr_t *)(uintptr_t) val;
if (!DTRACE_INSCRATCHPTR(&mstate,
(uintptr_t)memref, 2 * sizeof(uintptr_t))) {
*flags |= CPU_DTRACE_BADADDR;
continue;
}
/* Get the size from the memref. */
size = memref[1];