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bcb7825a77
The normalization pass in the sorting routine of the relative exception table serves two purposes: - it ensures that the address fields of the exception table entries are fully ordered, so that no ambiguities arise between entries with identical instruction offsets (i.e., when two instructions that are exactly 8 bytes apart each have an exception table entry associated with them) - it ensures that the offsets of both the instruction and the fixup fields of each entry are relative to their final location after sorting. Commiteb608fb366("s390/exceptions: switch to relative exception table entries") ported the relative exception table format from x86, but modified the sorting routine to only normalize the instruction offset field and not the fixup offset field. The result is that the fixup offset of each entry will be relative to the original location of the entry before sorting, likely leading to crashes when those entries are dereferenced. Fixes:eb608fb366("s390/exceptions: switch to relative exception table entries") Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: <stable@vger.kernel.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
86 lines
2.2 KiB
C
86 lines
2.2 KiB
C
#include <linux/module.h>
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#include <linux/sort.h>
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#include <asm/uaccess.h>
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/*
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* Search one exception table for an entry corresponding to the
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* given instruction address, and return the address of the entry,
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* or NULL if none is found.
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* We use a binary search, and thus we assume that the table is
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* already sorted.
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*/
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const struct exception_table_entry *
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search_extable(const struct exception_table_entry *first,
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const struct exception_table_entry *last,
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unsigned long value)
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{
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const struct exception_table_entry *mid;
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unsigned long addr;
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while (first <= last) {
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mid = ((last - first) >> 1) + first;
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addr = extable_insn(mid);
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if (addr < value)
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first = mid + 1;
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else if (addr > value)
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last = mid - 1;
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else
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return mid;
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}
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return NULL;
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}
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/*
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* The exception table needs to be sorted so that the binary
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* search that we use to find entries in it works properly.
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* This is used both for the kernel exception table and for
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* the exception tables of modules that get loaded.
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*
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*/
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static int cmp_ex(const void *a, const void *b)
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{
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const struct exception_table_entry *x = a, *y = b;
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/* This compare is only valid after normalization. */
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return x->insn - y->insn;
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}
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void sort_extable(struct exception_table_entry *start,
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struct exception_table_entry *finish)
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{
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struct exception_table_entry *p;
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int i;
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/* Normalize entries to being relative to the start of the section */
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for (p = start, i = 0; p < finish; p++, i += 8) {
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p->insn += i;
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p->fixup += i + 4;
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}
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sort(start, finish - start, sizeof(*start), cmp_ex, NULL);
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/* Denormalize all entries */
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for (p = start, i = 0; p < finish; p++, i += 8) {
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p->insn -= i;
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p->fixup -= i + 4;
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}
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}
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#ifdef CONFIG_MODULES
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/*
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* If the exception table is sorted, any referring to the module init
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* will be at the beginning or the end.
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*/
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void trim_init_extable(struct module *m)
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{
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/* Trim the beginning */
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while (m->num_exentries &&
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within_module_init(extable_insn(&m->extable[0]), m)) {
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m->extable++;
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m->num_exentries--;
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}
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/* Trim the end */
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while (m->num_exentries &&
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within_module_init(extable_insn(&m->extable[m->num_exentries-1]), m))
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m->num_exentries--;
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}
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#endif /* CONFIG_MODULES */
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