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XArray: Fix xa_find_next for large multi-index entries 

Coverity pointed out that xas_sibling() was shifting xa_offset without
promoting it to an unsigned long first, so the shift could cause an
overflow and we'd get the wrong answer.  The fix is obvious, and the
new test-case provokes UBSAN to report an error:
runtime error: shift exponent 60 is too large for 32-bit type 'int'

Fixes: 19c30f4dd0 ("XArray: Fix xa_find_after with multi-index entries")
Reported-by: Bjorn Helgaas <bhelgaas@google.com>
Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
alistair/sensors
Matthew Wilcox (Oracle) 2020-01-31 05:07:55 -05:00
parent d5226fa6db
commit bd40b17ca4
2 changed files with 20 additions and 1 deletions
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18
lib/test_xarray.c
View File

@ -12,6 +12,9 @@
static unsigned int tests_run;
static unsigned int tests_passed;
static const unsigned int order_limit =
IS_ENABLED(CONFIG_XARRAY_MULTI) ? BITS_PER_LONG : 1;
#ifndef XA_DEBUG
# ifdef __KERNEL__
void xa_dump(const struct xarray *xa) { }
@ -959,6 +962,20 @@ static noinline void check_multi_find_2(struct xarray *xa)
}
}
static noinline void check_multi_find_3(struct xarray *xa)
{
unsigned int order;
for (order = 5; order < order_limit; order++) {
unsigned long index = 1UL << (order - 5);
XA_BUG_ON(xa, !xa_empty(xa));
xa_store_order(xa, 0, order - 4, xa_mk_index(0), GFP_KERNEL);
XA_BUG_ON(xa, xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT));
xa_erase_index(xa, 0);
}
}
static noinline void check_find_1(struct xarray *xa)
{
unsigned long i, j, k;
@ -1081,6 +1098,7 @@ static noinline void check_find(struct xarray *xa)
for (i = 2; i < 10; i++)
check_multi_find_1(xa, i);
check_multi_find_2(xa);
check_multi_find_3(xa);
}
/* See find_swap_entry() in mm/shmem.c */

3
lib/xarray.c
View File

@ -1839,7 +1839,8 @@ static bool xas_sibling(struct xa_state *xas)
if (!node)
return false;
mask = (XA_CHUNK_SIZE << node->shift) - 1;
return (xas->xa_index & mask) > (xas->xa_offset << node->shift);
return (xas->xa_index & mask) >
((unsigned long)xas->xa_offset << node->shift);
}
/**