4.19-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 250f2da49cb8e582215a65c03f50e8ddf5cd119c ]
Syzkaller reported a OOB-read with the stacktrace below. This occurs inside __aa_lookupn_ns as `n` is not initialized. `n` is obtained from aa_splitn_fqname. In cases where `name` is invalid, aa_splitn_fqname returns without initializing `ns_name` and `ns_len`.
Fix this by always initializing `ns_name` and `ns_len`.
__dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 memcmp+0xe3/0x160 lib/string.c:861 strnstr+0x4b/0x70 lib/string.c:934 __aa_lookupn_ns+0xc1/0x570 security/apparmor/policy_ns.c:209 aa_lookupn_ns+0x88/0x1e0 security/apparmor/policy_ns.c:240 aa_fqlookupn_profile+0x1b9/0x1010 security/apparmor/policy.c:468 fqlookupn_profile+0x80/0xc0 security/apparmor/label.c:1844 aa_label_strn_parse+0xa3a/0x1230 security/apparmor/label.c:1908 aa_label_parse+0x42/0x50 security/apparmor/label.c:1943 aa_change_profile+0x513/0x3510 security/apparmor/domain.c:1362 apparmor_setprocattr+0xaa4/0x1150 security/apparmor/lsm.c:658 security_setprocattr+0x66/0xc0 security/security.c:1298 proc_pid_attr_write+0x301/0x540 fs/proc/base.c:2555 __vfs_write+0x119/0x9f0 fs/read_write.c:485 vfs_write+0x1fc/0x560 fs/read_write.c:549 ksys_write+0x101/0x260 fs/read_write.c:598 __do_sys_write fs/read_write.c:610 [inline] __se_sys_write fs/read_write.c:607 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:607 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fixes: 3b0aaf5866bf ("apparmor: add lib fn to find the "split" for fqnames") Reported-by: syzbot+61e4b490d9d2da591b50@syzkaller.appspotmail.com Signed-off-by: Zubin Mithra zsm@chromium.org Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: John Johansen john.johansen@canonical.com Signed-off-by: Sasha Levin sashal@kernel.org --- security/apparmor/lib.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/security/apparmor/lib.c b/security/apparmor/lib.c index 974affe50531..76491e7f4177 100644 --- a/security/apparmor/lib.c +++ b/security/apparmor/lib.c @@ -90,10 +90,12 @@ const char *aa_splitn_fqname(const char *fqname, size_t n, const char **ns_name, const char *end = fqname + n; const char *name = skipn_spaces(fqname, n);
- if (!name) - return NULL; *ns_name = NULL; *ns_len = 0; + + if (!name) + return NULL; + if (name[0] == ':') { char *split = strnchr(&name[1], end - &name[1], ':'); *ns_name = skipn_spaces(&name[1], end - &name[1]);