From 5a7b46b369419493bab4de67b1526e9f76b22a7f Mon Sep 17 00:00:00 2001 From: OGAWA Hirofumi Date: Thu, 20 Apr 2006 06:41:39 +0900 Subject: [PATCH] [PATCH] Add more prevent_tail_call() Those also break userland regs like following. 00000000 : 0: 0f b7 44 24 0c movzwl 0xc(%esp),%eax 5: 83 ca ff or $0xffffffff,%edx 8: 0f b7 4c 24 08 movzwl 0x8(%esp),%ecx d: 66 83 f8 ff cmp $0xffffffff,%ax 11: 0f 44 c2 cmove %edx,%eax 14: 66 83 f9 ff cmp $0xffffffff,%cx 18: 0f 45 d1 cmovne %ecx,%edx 1b: 89 44 24 0c mov %eax,0xc(%esp) 1f: 89 54 24 08 mov %edx,0x8(%esp) 23: e9 fc ff ff ff jmp 24 where the tailcall at the end overwrites the incoming stack-frame. Signed-off-by: OGAWA Hirofumi [ I would _really_ like to have a way to tell gcc about calling conventions. The "prevent_tail_call()" macro is pretty ugly ] Signed-off-by: Linus Torvalds --- kernel/uid16.c | 59 +++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 46 insertions(+), 13 deletions(-) diff --git a/kernel/uid16.c b/kernel/uid16.c index aa25605027..187e2a4238 100644 --- a/kernel/uid16.c +++ b/kernel/uid16.c @@ -20,43 +20,67 @@ asmlinkage long sys_chown16(const char __user * filename, old_uid_t user, old_gid_t group) { - return sys_chown(filename, low2highuid(user), low2highgid(group)); + long ret = sys_chown(filename, low2highuid(user), low2highgid(group)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_lchown16(const char __user * filename, old_uid_t user, old_gid_t group) { - return sys_lchown(filename, low2highuid(user), low2highgid(group)); + long ret = sys_lchown(filename, low2highuid(user), low2highgid(group)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_fchown16(unsigned int fd, old_uid_t user, old_gid_t group) { - return sys_fchown(fd, low2highuid(user), low2highgid(group)); + long ret = sys_fchown(fd, low2highuid(user), low2highgid(group)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setregid16(old_gid_t rgid, old_gid_t egid) { - return sys_setregid(low2highgid(rgid), low2highgid(egid)); + long ret = sys_setregid(low2highgid(rgid), low2highgid(egid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setgid16(old_gid_t gid) { - return sys_setgid(low2highgid(gid)); + long ret = sys_setgid(low2highgid(gid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setreuid16(old_uid_t ruid, old_uid_t euid) { - return sys_setreuid(low2highuid(ruid), low2highuid(euid)); + long ret = sys_setreuid(low2highuid(ruid), low2highuid(euid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setuid16(old_uid_t uid) { - return sys_setuid(low2highuid(uid)); + long ret = sys_setuid(low2highuid(uid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setresuid16(old_uid_t ruid, old_uid_t euid, old_uid_t suid) { - return sys_setresuid(low2highuid(ruid), low2highuid(euid), - low2highuid(suid)); + long ret = sys_setresuid(low2highuid(ruid), low2highuid(euid), + low2highuid(suid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_getresuid16(old_uid_t __user *ruid, old_uid_t __user *euid, old_uid_t __user *suid) @@ -72,8 +96,11 @@ asmlinkage long sys_getresuid16(old_uid_t __user *ruid, old_uid_t __user *euid, asmlinkage long sys_setresgid16(old_gid_t rgid, old_gid_t egid, old_gid_t sgid) { - return sys_setresgid(low2highgid(rgid), low2highgid(egid), - low2highgid(sgid)); + long ret = sys_setresgid(low2highgid(rgid), low2highgid(egid), + low2highgid(sgid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_getresgid16(old_gid_t __user *rgid, old_gid_t __user *egid, old_gid_t __user *sgid) @@ -89,12 +116,18 @@ asmlinkage long sys_getresgid16(old_gid_t __user *rgid, old_gid_t __user *egid, asmlinkage long sys_setfsuid16(old_uid_t uid) { - return sys_setfsuid(low2highuid(uid)); + long ret = sys_setfsuid(low2highuid(uid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } asmlinkage long sys_setfsgid16(old_gid_t gid) { - return sys_setfsgid(low2highgid(gid)); + long ret = sys_setfsgid(low2highgid(gid)); + /* avoid REGPARM breakage on x86: */ + prevent_tail_call(ret); + return ret; } static int groups16_to_user(old_gid_t __user *grouplist, -- 2.39.5