Re: [PATCH 14/24] init: clear root_wait on all invalid root= strings

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On 6/21/23 23:00, Christoph Hellwig wrote:
Hi Guenter,

can you try this patch?

diff --git a/block/early-lookup.c b/block/early-lookup.c
index a5be3c68ed079c..66e4514d671179 100644
--- a/block/early-lookup.c
+++ b/block/early-lookup.c
@@ -174,7 +174,7 @@ static int __init devt_from_devname(const char *name, dev_t *devt)
  	while (p > s && isdigit(p[-1]))
  		p--;
  	if (p == s || !*p || *p == '0')
-		return -EINVAL;
+		return -ENODEV;
/* try disk name without <part number> */
  	part = simple_strtoul(p, NULL, 10);

Not completely. Tests with root=/dev/sda still fail.

"name" passed to devt_from_devname() is "sda".

       for (p = s; *p; p++) {
                if (*p == '/')
                        *p = '!';
        }

advances 'p' to the end of the string.

        while (p > s && isdigit(p[-1]))
		p--;

moves it back to point to the first digit (if there is one).

        if (p == s || !*p || *p == '0')
		return -EINVAL;

then fails because *p is 0. In other words, the function only accepts
drive names with digits at the end (and the first digit must not be '0').

I don't recall how I hit the other condition earlier. I have various
"/dev/mmcblkX" in my tests, where X can be any number including 0.
Maybe those fail randomly as well.

Overall I am not sure though what an "invalid" devicename is supposed
to be in this context. I have "sda", "sr0", "vda", "mtdblkX",
"nvme0n1", "mmcblkX", and "hda". Why would any of those not be eligible
for "rootwait" ?

In practice, everything not ending with a digit, or ending with
'0', fails the first test. Everything ending with a digit > 0
fails the second test. But "humptydump3p4" passes all those tests.

Guenter

---
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

#define EINVAL1	1
#define EINVAL2	2
#define EINVAL3	3
#define ENODEV	4

static int devt_from_devname(const char *name)
{
        int part;
        char s[32];
        char *p;

        if (strlen(name) > 31)
                return EINVAL1;

        strcpy(s, name);
        for (p = s; *p; p++) {
                if (*p == '/')
                        *p = '!';
        }

        /*
         * Try non-existent, but valid partition, which may only exist after
         * opening the device, like partitioned md devices.
         */
        while (p > s && isdigit(p[-1]))
                p--;
        if (p == s || !*p || *p == '0') {
                return EINVAL2;
        }

        /* try disk name without <part number> */
        part = strtoul(p, NULL, 10);
        *p = '\0';

        /* try disk name without p<part number> */
        if (p < s + 2 || !isdigit(p[-2]) || p[-1] != 'p') {
                return EINVAL3;
        }
        return ENODEV;
}

char *devnames[] = {
    "sda",
    "sda1",
    "mmcblk0",
    "mmcblk1",
    "mtdblk0",
    "mtdblk1",
    "vda",
    "hda",
    "nvme0n1",
    "sr0",
    "sr1",
    "humptydump3p4",
    NULL
};

int main(int argc, char **argv)
{
	char *str;
	int i;

	for (i = 0, str = devnames[0]; str; str = devnames[++i]) {
	    printf("%s: %d\n", str, devt_from_devname(str));
	}
}

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