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Revision 447ac906e189535e77dcb1f4bbe3f1bc917d4c12 authored by Patrick Steinhardt on 01 December 2022, 14:45:31 UTC, committed by Junio C Hamano on 05 December 2022, 06:14:16 UTC 
attr: fix out-of-bounds read with unreasonable amount of patterns
 
The `struct attr_stack` tracks the stack of all patterns together with
their attributes. When parsing a gitattributes file that has more than
2^31 such patterns though we may trigger multiple out-of-bounds reads on
64 bit platforms. This is because while the `num_matches` variable is an
unsigned integer, we always use a signed integer to iterate over them.

I have not been able to reproduce this issue due to memory constraints
on my systems. But despite the out-of-bounds reads, the worst thing that
can seemingly happen is to call free(3P) with a garbage pointer when
calling `attr_stack_free()`.

Fix this bug by using unsigned integers to iterate over the array. While
this makes the iteration somewhat awkward when iterating in reverse, it
is at least better than knowingly running into an out-of-bounds read.
While at it, convert the call to `ALLOC_GROW` to use `ALLOC_GROW_BY`
instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 34ace8b
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prio-queue.h 
#ifndef PRIO_QUEUE_H
#define PRIO_QUEUE_H

/*
 * A priority queue implementation, primarily for keeping track of
 * commits in the 'date-order' so that we process them from new to old
 * as they are discovered, but can be used to hold any pointer to
 * struct.  The caller is responsible for supplying a function to
 * compare two "things".
 *
 * Alternatively, this data structure can also be used as a LIFO stack
 * by specifying NULL as the comparison function.
 */

/*
 * Compare two "things", one and two; the third parameter is cb_data
 * in the prio_queue structure.  The result is returned as a sign of
 * the return value, being the same as the sign of the result of
 * subtracting "two" from "one" (i.e. negative if "one" sorts earlier
 * than "two").
 */
typedef int (*prio_queue_compare_fn)(const void *one, const void *two, void *cb_data);

struct prio_queue_entry {
	unsigned ctr;
	void *data;
};

struct prio_queue {
	prio_queue_compare_fn compare;
	unsigned insertion_ctr;
	void *cb_data;
	int alloc, nr;
	struct prio_queue_entry *array;
};

/*
 * Add the "thing" to the queue.
 */
void prio_queue_put(struct prio_queue *, void *thing);

/*
 * Extract the "thing" that compares the smallest out of the queue,
 * or NULL.  If compare function is NULL, the queue acts as a LIFO
 * stack.
 */
void *prio_queue_get(struct prio_queue *);

/*
 * Gain access to the "thing" that would be returned by
 * prio_queue_get, but do not remove it from the queue.
 */
void *prio_queue_peek(struct prio_queue *);

void clear_prio_queue(struct prio_queue *);

/* Reverse the LIFO elements */
void prio_queue_reverse(struct prio_queue *);

#endif /* PRIO_QUEUE_H */
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