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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
Raw File
xdiff-interface.h 
#ifndef XDIFF_INTERFACE_H
#define XDIFF_INTERFACE_H

#include "cache.h"
#include "xdiff/xdiff.h"

/*
 * xdiff isn't equipped to handle content over a gigabyte;
 * we make the cutoff 1GB - 1MB to give some breathing
 * room for constant-sized additions (e.g., merge markers)
 */
#define MAX_XDIFF_SIZE (1024UL * 1024 * 1023)

typedef void (*xdiff_emit_line_fn)(void *, char *, unsigned long);
typedef void (*xdiff_emit_hunk_fn)(void *data,
				   long old_begin, long old_nr,
				   long new_begin, long new_nr,
				   const char *func, long funclen);

int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *ecb);
int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
		  xdiff_emit_hunk_fn hunk_fn,
		  xdiff_emit_line_fn line_fn,
		  void *consume_callback_data,
		  xpparam_t const *xpp, xdemitconf_t const *xecfg);
int read_mmfile(mmfile_t *ptr, const char *filename);
void read_mmblob(mmfile_t *ptr, const struct object_id *oid);
int buffer_is_binary(const char *ptr, unsigned long size);

void xdiff_set_find_func(xdemitconf_t *xecfg, const char *line, int cflags);
void xdiff_clear_find_func(xdemitconf_t *xecfg);
int git_xmerge_config(const char *var, const char *value, void *cb);
extern int git_xmerge_style;

/*
 * Can be used as a no-op hunk_fn for xdi_diff_outf(), since a NULL
 * one just sends the hunk line to the line_fn callback).
 */
void discard_hunk_line(void *priv,
		       long ob, long on, long nb, long nn,
		       const char *func, long funclen);

/*
 * Compare the strings l1 with l2 which are of size s1 and s2 respectively.
 * Returns 1 if the strings are deemed equal, 0 otherwise.
 * The `flags` given as XDF_WHITESPACE_FLAGS determine how white spaces
 * are treated for the comparison.
 */
int xdiff_compare_lines(const char *l1, long s1,
			const char *l2, long s2, long flags);

/*
 * Returns a hash of the string s of length len.
 * The `flags` given as XDF_WHITESPACE_FLAGS determine how white spaces
 * are treated for the hash.
 */
unsigned long xdiff_hash_string(const char *s, size_t len, long flags);

#endif
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