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LSM: general protection fault in legacy_parse_param 

The usual LSM hook "bail on fail" scheme doesn't work for cases where
a security module may return an error code indicating that it does not
recognize an input.  In this particular case Smack sees a mount option
that it recognizes, and returns 0. A call to a BPF hook follows, which
returns -ENOPARAM, which confuses the caller because Smack has processed
its data.

The SELinux hook incorrectly returns 1 on success. There was a time
when this was correct, however the current expectation is that it
return 0 on success. This is repaired.

Reported-by: syzbot+d1e3b1d92d25abf97943@syzkaller.appspotmail.com
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Casey Schaufler 2022-01-27 04:51:00 +00:00 committed by Paul Moore
parent cdeea45422
commit ecff30575b
2 changed files with 17 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
security/security.c
View File

@ -884,9 +884,22 @@ int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
return call_int_hook(fs_context_dup, 0, fc, src_fc);
}
int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param)
int security_fs_context_parse_param(struct fs_context *fc,
struct fs_parameter *param)
{
return call_int_hook(fs_context_parse_param, -ENOPARAM, fc, param);
struct security_hook_list *hp;
int trc;
int rc = -ENOPARAM;
hlist_for_each_entry(hp, &security_hook_heads.fs_context_parse_param,
list) {
trc = hp->hook.fs_context_parse_param(fc, param);
if (trc == 0)
rc = 0;
else if (trc != -ENOPARAM)
return trc;
}
return rc;
}
int security_sb_alloc(struct super_block *sb)

5
security/selinux/hooks.c
View File

@ -2859,10 +2859,9 @@ static int selinux_fs_context_parse_param(struct fs_context *fc,
return opt;
rc = selinux_add_opt(opt, param->string, &fc->security);
if (!rc) {
if (!rc)
param->string = NULL;
rc = 1;
}
return rc;
}