From: Jan Beulich <jbeulich-IBi9RG/b67k@public.gmane.org>
To: David Gibson
<david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>,
Jon Loeliger <jdl-CYoMK+44s/E@public.gmane.org>
Cc: devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: [PATCH] libfdt: fix undefined behaviour in fdt_splice_()
Date: Thu, 5 Mar 2020 15:04:45 +0100 [thread overview]
Message-ID: <f2d09e81-7cb8-c5cc-9699-1ac05b0626ff@suse.com> (raw)
libfdt: fix undefined behaviour in fdt_splice_()
Along the lines of commit d0b3ab0a0f46 ("libfdt: Fix undefined behaviour
in fdt_offset_ptr()"), fdt_splice_() similarly may not use pointer
arithmetic to do overflow checks. (The left side of the checks added by
d4c7c25c9ed1 ["libfdt: check for potential overrun in _fdt_splice()"]
doesn't really lend itself to similar replacement though.)
Signed-off-by: Jan Beulich <jbeulich-IBi9RG/b67k@public.gmane.org>
---
The right side of the checks added by d4c7c25c9ed1 looks suspicious,
which is more noticable after the transformation done here:
end - oldlen + newlen < (char *)fdt
end - (char *)fdt + newlen < oldlen
dsize + newlen < oldlen
--- a/libfdt/fdt_rw.c
+++ b/libfdt/fdt_rw.c
@@ -46,7 +46,7 @@ static int fdt_rw_probe_(void *fdt)
return err_; \
}
-static inline int fdt_data_size_(void *fdt)
+static inline unsigned int fdt_data_size_(void *fdt)
{
return fdt_off_dt_strings(fdt) + fdt_size_dt_strings(fdt);
}
@@ -54,15 +54,16 @@ static inline int fdt_data_size_(void *f
static int fdt_splice_(void *fdt, void *splicepoint, int oldlen, int newlen)
{
char *p = splicepoint;
- char *end = (char *)fdt + fdt_data_size_(fdt);
+ unsigned int dsize = fdt_data_size_(fdt);
+ size_t soff = p - (char *)fdt;
- if (((p + oldlen) < p) || ((p + oldlen) > end))
+ if ((oldlen < 0) || (soff + oldlen < soff) || (soff + oldlen > dsize))
return -FDT_ERR_BADOFFSET;
- if ((p < (char *)fdt) || ((end - oldlen + newlen) < (char *)fdt))
+ if ((p < (char *)fdt) || (dsize + newlen < oldlen))
return -FDT_ERR_BADOFFSET;
- if ((end - oldlen + newlen) > ((char *)fdt + fdt_totalsize(fdt)))
+ if (dsize - oldlen + newlen > fdt_totalsize(fdt))
return -FDT_ERR_NOSPACE;
- memmove(p + newlen, p + oldlen, end - p - oldlen);
+ memmove(p + newlen, p + oldlen, ((char *)fdt + dsize) - (p + oldlen));
return 0;
}
next reply other threads:[~2020-03-05 14:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-05 14:04 Jan Beulich [this message]
[not found] ` <f2d09e81-7cb8-c5cc-9699-1ac05b0626ff-IBi9RG/b67k@public.gmane.org>
2020-03-11 4:59 ` [PATCH] libfdt: fix undefined behaviour in fdt_splice_() David Gibson
[not found] ` <20200311045914.GY660117-K0bRW+63XPQe6aEkudXLsA@public.gmane.org>
2020-03-12 8:19 ` Jan Beulich
[not found] ` <4eaa4349-edbf-eb53-637d-b62a20befddd-IBi9RG/b67k@public.gmane.org>
2020-03-13 0:24 ` David Gibson
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