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libfdt: fix undefined behaviour in fdt_splice_() 

libfdt: fix undefined behaviour in fdt_splice_()

Along the lines of commit d0b3ab0a0f ("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
d4c7c25c9e ["libfdt: check for potential overrun in _fdt_splice()"]
doesn't really lend itself to similar replacement though.)

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Message-Id: <f2d09e81-7cb8-c5cc-9699-1ac05b0626ff@suse.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Jan Beulich 2020-03-05 15:04:45 +01:00 committed by David Gibson
parent 2525da3dba
commit 73d6e9ecb4
1 changed files with 7 additions and 6 deletions
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13
libfdt/fdt_rw.c
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@ -46,7 +46,7 @@ static int fdt_rw_probe_(void *fdt)
return err_; \ 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); return fdt_off_dt_strings(fdt) + fdt_size_dt_strings(fdt);
} }
@ -54,15 +54,16 @@ static inline int fdt_data_size_(void *fdt)
static int fdt_splice_(void *fdt, void *splicepoint, int oldlen, int newlen) static int fdt_splice_(void *fdt, void *splicepoint, int oldlen, int newlen)
{ {
char *p = splicepoint; 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; return -FDT_ERR_BADOFFSET;
if ((p < (char *)fdt) || ((end - oldlen + newlen) < (char *)fdt)) if ((p < (char *)fdt) || (dsize + newlen < oldlen))
return -FDT_ERR_BADOFFSET; return -FDT_ERR_BADOFFSET;
if ((end - oldlen + newlen) > ((char *)fdt + fdt_totalsize(fdt))) if (dsize - oldlen + newlen > fdt_totalsize(fdt))
return -FDT_ERR_NOSPACE; return -FDT_ERR_NOSPACE;
memmove(p + newlen, p + oldlen, end - p - oldlen); memmove(p + newlen, p + oldlen, ((char *)fdt + dsize) - (p + oldlen));
return 0; return 0;
} }