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authorAlyssa Ross <hi@alyssa.is>2021-09-15 22:11:55 +0000
committerRich Felker <dalias@aerifal.cx>2022-05-15 19:19:42 -0400
commit751bee0ee727e8d8b003c87cff77ac76f1dbecd6 (patch)
treee714f49ea914ba7560c2b22a3ef4ec6a371cbfb8 /src
parentdcb31f6b450fdeed4dc364e15cd190e8562ea227 (diff)
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mntent: fix parsing lines with optional fields
According to fstab(5), the last two fields are optional, but this wasn't accepted. After this change, only the first field is required, which matches glibc's behaviour. Using sscanf as before, it would have been impossible to differentiate between 0 fields and 4 fields, because sscanf would have returned 0 in both cases due to the use of assignment suppression and %n for the string fields (which is important to avoid copying any strings). So instead, before calling sscanf, initialize every string to the empty string, and then we can check which strings are empty afterwards to know how many fields were matched.
Diffstat (limited to 'src')
-rw-r--r--src/misc/mntent.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/src/misc/mntent.c b/src/misc/mntent.c
index eabb8200..962b8767 100644
--- a/src/misc/mntent.c
+++ b/src/misc/mntent.c
@@ -21,7 +21,8 @@ int endmntent(FILE *f)
struct mntent *getmntent_r(FILE *f, struct mntent *mnt, char *linebuf, int buflen)
{
- int cnt, n[8], use_internal = (linebuf == SENTINEL);
+ int n[8], use_internal = (linebuf == SENTINEL);
+ size_t len, i;
mnt->mnt_freq = 0;
mnt->mnt_passno = 0;
@@ -39,10 +40,13 @@ struct mntent *getmntent_r(FILE *f, struct mntent *mnt, char *linebuf, int bufle
errno = ERANGE;
return 0;
}
- cnt = sscanf(linebuf, " %n%*s%n %n%*s%n %n%*s%n %n%*s%n %d %d",
+
+ len = strlen(linebuf);
+ for (i = 0; i < sizeof n / sizeof *n; i++) n[i] = len;
+ sscanf(linebuf, " %n%*s%n %n%*s%n %n%*s%n %n%*s%n %d %d",
n, n+1, n+2, n+3, n+4, n+5, n+6, n+7,
&mnt->mnt_freq, &mnt->mnt_passno);
- } while (cnt < 2 || linebuf[n[0]] == '#');
+ } while (linebuf[n[0]] == '#' || n[1]==len);
linebuf[n[1]] = 0;
linebuf[n[3]] = 0;