From 1056e5b4c3f2d90ed2b4a55f96add28da2f4c8fa Mon Sep 17 00:00:00 2001 From: Siddhesh Poyarekar Date: Tue, 19 Sep 2023 18:39:32 -0400 Subject: tunables: Terminate if end of input is reached (CVE-2023-4911) The string parsing routine may end up writing beyond bounds of tunestr if the input tunable string is malformed, of the form name=name=val. This gets processed twice, first as name=name=val and next as name=val, resulting in tunestr being name=name=val:name=val, thus overflowing tunestr. Terminate the parsing loop at the first instance itself so that tunestr does not overflow. This also fixes up tst-env-setuid-tunables to actually handle failures correct and add new tests to validate the fix for this CVE. Signed-off-by: Siddhesh Poyarekar Reviewed-by: Carlos O'Donell --- elf/dl-tunables.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) (limited to 'elf/dl-tunables.c') diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c index 62b7332..cae67ef 100644 --- a/elf/dl-tunables.c +++ b/elf/dl-tunables.c @@ -180,11 +180,7 @@ parse_tunables (char *tunestr, char *valstring) /* If we reach the end of the string before getting a valid name-value pair, bail out. */ if (p[len] == '\0') - { - if (__libc_enable_secure) - tunestr[off] = '\0'; - return; - } + break; /* We did not find a valid name-value pair before encountering the colon. */ @@ -244,9 +240,16 @@ parse_tunables (char *tunestr, char *valstring) } } - if (p[len] != '\0') - p += len + 1; + /* We reached the end while processing the tunable string. */ + if (p[len] == '\0') + break; + + p += len + 1; } + + /* Terminate tunestr before we leave. */ + if (__libc_enable_secure) + tunestr[off] = '\0'; } /* Enable the glibc.malloc.check tunable in SETUID/SETGID programs only when -- cgit v1.1