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In r331279 the code used ENOSYS to check the existence of getrandom(2).

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This will only work if the caller already handles SIGSYS, which is not
always the case.

Address this by checking osreldate instead. Note that because there
was not __FreeBSD_version bump when the system call was added, use
1200061 (r332100) which is the first bump after the introduction of
the system call.

PR:		230762
Reported by:	Jenkins via Mark Millard
Reviewed by:	cem
Differential Revision:	https://reviews.freebsd.org/D16807
This commit is contained in:
Xin LI 2018-08-20 02:17:55 +00:00
parent beacffb30d
commit 59488f25ad
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=338084
1 changed files with 29 additions and 8 deletions
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37
lib/libc/gen/getentropy.c
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@ -34,10 +34,14 @@ __FBSDID("$FreeBSD$");
#include <sys/sysctl.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include "libc_private.h"
/* First __FreeBSD_version bump after introduction of getrandom(2) (r331279) */
#define GETRANDOM_FIRST 1200061
extern int __sysctl(int *, u_int, void *, size_t *, void *, size_t);
static size_t
@ -99,21 +103,38 @@ int
getentropy(void *buf, size_t buflen)
{
ssize_t rd;
bool have_getrandom;
if (buflen > 256) {
errno = EIO;
return (-1);
}
have_getrandom = (__getosreldate() >= GETRANDOM_FIRST);
while (buflen > 0) {
rd = getrandom(buf, buflen, 0);
if (rd == -1) {
if (errno == EINTR)
continue;
else if (errno == ENOSYS || errno == ECAPMODE)
return (getentropy_fallback(buf, buflen));
else
return (-1);
if (have_getrandom) {
rd = getrandom(buf, buflen, 0);
if (rd == -1) {
switch (errno) {
case ECAPMODE:
/*
* Kernel >= r331280 and < r337999
* will return ECAPMODE when the
* caller is already in capability
* mode, fallback to traditional
* method in this case.
*/
have_getrandom = false;
continue;
case EINTR:
continue;
default:
return (-1);
}
}
} else {
return (getentropy_fallback(buf, buflen));
}
/* This cannot happen. */