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Change umovestr API: return > 0 instead of 0 if NUL was seen

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* pathtrace.c (upathmatch): Adjust umovestr return value check for new API.
* util.c (printpathn): Use umovestr() > 0 return value for more efficient
(and robust - we don't depend on "no overwrote past NUL" behavior anymore)
handling of terminating NUL.
(printstr): Remove useless NUL placement before umovestr() call.
Allocate 1 byte more to outstr[] array - for NUL.
(umovestr): Change to return 1 if NUL was seen.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2012-01-20 11:56:00 +01:00
parent a17e55ca8f
commit 6cecba5322
2 changed files with 27 additions and 17 deletions
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2
pathtrace.c
View File

@ -68,7 +68,7 @@ upathmatch(struct tcb *tcp, unsigned long upath)
{
char path[PATH_MAX + 1];
return umovestr(tcp, upath, sizeof path, path) == 0 &&
return umovestr(tcp, upath, sizeof path, path) >= 0 &&
pathmatch(path);
}

42
util.c
View File

@ -432,6 +432,9 @@ printuid(const char *text, unsigned long uid)
* Write up to (3 + `size' * 4) bytes to `outstr' buffer.
* If `len' < 0, treat `instr' as a NUL-terminated string
* and quote at most (`size' - 1) bytes.
*
* Returns 0 if len < 0 and NUL was seen, 1 otherwise.
* Note that if len >= 0, always returns 1.
*/
static int
string_quote(const char *instr, char *outstr, int len, int size)
@ -565,32 +568,30 @@ void
printpathn(struct tcb *tcp, long addr, int n)
{
char path[MAXPATHLEN + 1];
int nul_seen;
if (!addr) {
tprints("NULL");
return;
}
/* Cap path length to the path buffer size,
and NUL-terminate the buffer. */
/* Cap path length to the path buffer size */
if (n > sizeof path - 1)
n = sizeof path - 1;
path[n] = '\0';
/* Fetch one byte more to find out whether path length > n. */
if (umovestr(tcp, addr, n + 1, path) < 0)
nul_seen = umovestr(tcp, addr, n + 1, path);
if (nul_seen < 0)
tprintf("%#lx", addr);
else {
char *outstr;
int trunc = (path[n] != '\0');
if (trunc)
path[n] = '\0';
path[n] = '\0';
n++;
outstr = alloca(4 * n); /* 4*(n-1) + 2 for quotes */
outstr = alloca(4 * n); /* 4*(n-1) + 3 for quotes and NUL */
string_quote(path, outstr, -1, n);
tprints(outstr);
if (trunc)
if (!nul_seen)
tprints("...");
}
}
@ -624,7 +625,7 @@ printstr(struct tcb *tcp, long addr, int len)
str = malloc(max_strlen + 1);
if (!str)
die_out_of_memory();
outstr = malloc(4 * max_strlen + /*for quotes:*/ 2);
outstr = malloc(4 * max_strlen + /*for quotes and NUL:*/ 3);
if (!outstr)
die_out_of_memory();
}
@ -635,8 +636,6 @@ printstr(struct tcb *tcp, long addr, int len)
* because string_quote() quotes one byte less.
*/
size = max_strlen + 1;
str[max_strlen] = '\0';
/* FIXME! umovestr can overwrite the '\0' stored above??? */
if (umovestr(tcp, addr, size, str) < 0) {
tprintf("%#lx", addr);
return;
@ -650,6 +649,9 @@ printstr(struct tcb *tcp, long addr, int len)
}
}
/* If string_quote didn't see NUL and (it was supposed to be ASCIZ str
* or we were requested to print more than -s NUM chars)...
*/
ellipsis = (string_quote(str, outstr, len, size) &&
(len < 0 || len > max_strlen));
@ -859,8 +861,16 @@ umoven(struct tcb *tcp, long addr, int len, char *laddr)
}
/*
* like `umove' but make the additional effort of looking
* Like `umove' but make the additional effort of looking
* for a terminating zero byte.
*
* Returns < 0 on error, > 0 if NUL was seen,
* (TODO if useful: return count of bytes including NUL),
* else 0 if len bytes were read but no NUL byte seen.
*
* Note: there is no guarantee we won't overwrite some bytes
* in laddr[] _after_ terminating NUL (but, of course,
* we never write past laddr[len-1]).
*/
int
umovestr(struct tcb *tcp, long addr, int len, char *laddr)
@ -891,7 +901,7 @@ umovestr(struct tcb *tcp, long addr, int len, char *laddr)
if (move <= 0)
return left != len ? 0 : -1;
if (memchr(laddr, 0, move))
break;
return 1;
left -= move;
laddr += move;
addr += move;
@ -926,7 +936,7 @@ umovestr(struct tcb *tcp, long addr, int len, char *laddr)
memcpy(laddr, &u.x[n], m = MIN(sizeof(long)-n, len));
while (n & (sizeof(long) - 1))
if (u.x[n++] == '\0')
return 0;
return 1;
addr += sizeof(long), laddr += m, len -= m;
}
while (len) {
@ -945,7 +955,7 @@ umovestr(struct tcb *tcp, long addr, int len, char *laddr)
memcpy(laddr, u.x, m = MIN(sizeof(long), len));
for (i = 0; i < sizeof(long); i++)
if (u.x[i] == '\0')
return 0;
return 1;
addr += sizeof(long), laddr += m, len -= m;
}