* Re: KASAN: use-after-free Read in tomoyo_realpath_from_path [not found] <0000000000004f43fa058a97f4d3@google.com> @ 2019-06-06 2:08 ` Tetsuo Handa 2019-06-06 5:20 ` Tetsuo Handa 1 sibling, 0 replies; 11+ messages in thread From: Tetsuo Handa @ 2019-06-06 2:08 UTC (permalink / raw) To: Al Viro, linux-fsdevel Cc: syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn Here is a reproducer. The problem is that TOMOYO is accessing already freed socket from security_file_open() which later fails with -ENXIO (because we can't get file descriptor of sockets via /proc/pid/fd/n interface), and the file descriptor is getting released before security_file_open() completes because we do not raise "struct file"->f_count of the file which is accessible via /proc/pid/fd/n interface. We can avoid this problem if we can avoid calling security_file_open() which after all fails with -ENXIO. How should we handle this race? Let LSM modules check if security_file_open() was called on a socket? ---------------------------------------- diff --git a/fs/open.c b/fs/open.c index b5b80469b93d..995ffcb37128 100644 --- a/fs/open.c +++ b/fs/open.c @@ -765,6 +765,12 @@ static int do_dentry_open(struct file *f, error = security_file_open(f); if (error) goto cleanup_all; + if (!strcmp(current->comm, "a.out") && + f->f_path.dentry->d_sb->s_magic == SOCKFS_MAGIC) { + printk("Start open(socket) delay\n"); + schedule_timeout_killable(HZ * 5); + printk("End open(socket) delay\n"); + } error = break_lease(locks_inode(f), f->f_flags); if (error) ---------------------------------------- ---------------------------------------- #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <sys/socket.h> int main(int argc, char *argv[]) { pid_t pid = getpid(); int fd = socket(AF_ISDN, SOCK_RAW, 0); char buffer[128] = { }; if (fork() == 0) { close(fd); snprintf(buffer, sizeof(buffer) - 1, "/proc/%u/fd/%u", pid, fd); open(buffer, 3); _exit(0); } sleep(2); close(fd); return 0; } ---------------------------------------- ---------------------------------------- getpid() = 32504 socket(AF_ISDN, SOCK_RAW, 0) = 3 clone(strace: Process 32505 attached child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7efea30dda10) = 32505 [pid 32504] rt_sigprocmask(SIG_BLOCK, [CHLD], <unfinished ...> [pid 32505] close(3 <unfinished ...> [pid 32504] <... rt_sigprocmask resumed> [], 8) = 0 [pid 32505] <... close resumed> ) = 0 [pid 32504] rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0 [pid 32505] open("/proc/32504/fd/3", O_ACCMODE <unfinished ...> [pid 32504] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 [pid 32504] nanosleep({2, 0}, 0x7ffd3c608150) = 0 [pid 32504] close(3) = 0 [pid 32504] exit_group(0) = ? [pid 32504] +++ exited with 0 +++ <... open resumed> ) = -1 ENXIO (No such device or address) exit_group(0) = ? ---------------------------------------- ---------------------------------------- [ 95.109628] Start open(socket) delay [ 97.113150] base_sock_release(00000000506a3239) sk=00000000016d0ceb [ 100.142235] End open(socket) delay ---------------------------------------- ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: KASAN: use-after-free Read in tomoyo_realpath_from_path [not found] <0000000000004f43fa058a97f4d3@google.com> 2019-06-06 2:08 ` KASAN: use-after-free Read in tomoyo_realpath_from_path Tetsuo Handa @ 2019-06-06 5:20 ` Tetsuo Handa 2019-06-09 6:41 ` [PATCH] tomoyo: Don't check open/getattr permission on sockets Tetsuo Handa 1 sibling, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-06-06 5:20 UTC (permalink / raw) To: Al Viro, linux-fsdevel Cc: syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn Tetsuo Handa wrote: > The problem is that TOMOYO is accessing already freed socket from security_file_open() > which later fails with -ENXIO (because we can't get file descriptor of sockets via > /proc/pid/fd/n interface), and the file descriptor is getting released before > security_file_open() completes because we do not raise "struct file"->f_count of > the file which is accessible via /proc/pid/fd/n interface. We can avoid this problem > if we can avoid calling security_file_open() which after all fails with -ENXIO. > How should we handle this race? Let LSM modules check if security_file_open() was > called on a socket? Well, just refusing security_file_open() is not sufficient, for open(O_PATH) allows installing file descriptor where SOCKET_I(inode)->sk can change at any moment, and TOMOYO cannot tell whether it is safe to access SOCKET_I(inode)->sk from security_inode_getattr(). But refusing open(O_PATH) as well might break userspace programs. Oh, no... ---------------------------------------- diff --git a/fs/open.c b/fs/open.c index b5b80469b93d..ea69668e2cd8 100644 --- a/fs/open.c +++ b/fs/open.c @@ -728,6 +728,16 @@ static int do_dentry_open(struct file *f, /* Ensure that we skip any errors that predate opening of the file */ f->f_wb_err = filemap_sample_wb_err(f->f_mapping); + /* + * Sockets must not be opened via /proc/pid/fd/n, even with O_PATH, + * for SOCKET_I(inode)->sk can be kfree()d at any moment after a file + * descriptor obtained by opening /proc/pid/fd/n was installed. + */ + if (unlikely(S_ISSOCK(inode->i_mode))) { + error = (f->f_flags & O_PATH) ? -ENOENT : -ENXIO; + goto cleanup_file; + } + if (unlikely(f->f_flags & O_PATH)) { f->f_mode = FMODE_PATH | FMODE_OPENED; f->f_op = &empty_fops; ---------------------------------------- ---------------------------------------- #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <sys/socket.h> int main(int argc, char *argv[]) { pid_t pid = getpid(); int fd = socket(AF_INET, SOCK_STREAM, 0); char buffer[128] = { }; if (fork() == 0) { struct stat buf = { }; close(fd); snprintf(buffer, sizeof(buffer) - 1, "/proc/%u/fd/%u", pid, fd); fd = open(buffer, __O_PATH); sleep(5); fstat(fd, &buf); _exit(0); } sleep(2); close(fd); return 0; } ---------------------------------------- ^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH] tomoyo: Don't check open/getattr permission on sockets. 2019-06-06 5:20 ` Tetsuo Handa @ 2019-06-09 6:41 ` Tetsuo Handa 2019-06-16 6:49 ` Tetsuo Handa 0 siblings, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-06-09 6:41 UTC (permalink / raw) To: Al Viro, linux-fsdevel Cc: syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn syzbot is reporting that use of SOCKET_I()->sk from open() can result in use after free problem [1], for socket's inode is still reachable via /proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed. But there is no point with calling security_file_open() on sockets because open("/proc/pid/fd/n", !O_PATH) on sockets fails with -ENXIO. There is some point with calling security_inode_getattr() on sockets because stat("/proc/pid/fd/n") and fstat(open("/proc/pid/fd/n", O_PATH)) are valid. If we want to access "struct sock"->sk_{family,type,protocol} fields, we will need to use security_socket_post_create() hook and security_inode_free() hook in order to remember these fields because security_sk_free() hook is called before the inode is destructed. But since information which can be protected by checking security_inode_getattr() on sockets is trivial, let's not be bothered by "struct inode"->i_security management. There is point with calling security_file_ioctl() on sockets. Since ioctl(open("/proc/pid/fd/n", O_PATH)) is invalid, security_file_ioctl() on sockets should remain safe. [1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74 Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com> --- security/tomoyo/tomoyo.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 716c92e..9661b86 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -126,6 +126,9 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) */ static int tomoyo_inode_getattr(const struct path *path) { + /* It is not safe to call tomoyo_get_socket_name(). */ + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) + return 0; return tomoyo_path_perm(TOMOYO_TYPE_GETATTR, path, NULL); } @@ -316,6 +319,10 @@ static int tomoyo_file_open(struct file *f) /* Don't check read permission here if called from do_execve(). */ if (current->in_execve) return 0; + /* Sockets can't be opened by open(). */ + if (f->f_path.dentry->d_inode && + S_ISSOCK(f->f_path.dentry->d_inode->i_mode)) + return 0; return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, f->f_flags); } -- 1.8.3.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH] tomoyo: Don't check open/getattr permission on sockets. 2019-06-09 6:41 ` [PATCH] tomoyo: Don't check open/getattr permission on sockets Tetsuo Handa @ 2019-06-16 6:49 ` Tetsuo Handa 2019-06-18 20:49 ` Al Viro 0 siblings, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-06-16 6:49 UTC (permalink / raw) To: Al Viro, linux-fsdevel Cc: syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller Hello, Al. Q1: Do you agree that we should fix TOMOYO side rather than SOCKET_I()->sk management. Q2: Do you see any problem with using f->f_path.dentry->d_inode ? Do we need to use d_backing_inode() or d_inode() ? Regards. On 2019/06/09 15:41, Tetsuo Handa wrote: > syzbot is reporting that use of SOCKET_I()->sk from open() can result in > use after free problem [1], for socket's inode is still reachable via > /proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed. > > But there is no point with calling security_file_open() on sockets > because open("/proc/pid/fd/n", !O_PATH) on sockets fails with -ENXIO. > > There is some point with calling security_inode_getattr() on sockets > because stat("/proc/pid/fd/n") and fstat(open("/proc/pid/fd/n", O_PATH)) > are valid. If we want to access "struct sock"->sk_{family,type,protocol} > fields, we will need to use security_socket_post_create() hook and > security_inode_free() hook in order to remember these fields because > security_sk_free() hook is called before the inode is destructed. But > since information which can be protected by checking > security_inode_getattr() on sockets is trivial, let's not be bothered by > "struct inode"->i_security management. > > There is point with calling security_file_ioctl() on sockets. Since > ioctl(open("/proc/pid/fd/n", O_PATH)) is invalid, security_file_ioctl() > on sockets should remain safe. > > [1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74 > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > Reported-by: syzbot <syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com> > --- > security/tomoyo/tomoyo.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c > index 716c92e..9661b86 100644 > --- a/security/tomoyo/tomoyo.c > +++ b/security/tomoyo/tomoyo.c > @@ -126,6 +126,9 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) > */ > static int tomoyo_inode_getattr(const struct path *path) > { > + /* It is not safe to call tomoyo_get_socket_name(). */ > + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) > + return 0; > return tomoyo_path_perm(TOMOYO_TYPE_GETATTR, path, NULL); > } > > @@ -316,6 +319,10 @@ static int tomoyo_file_open(struct file *f) > /* Don't check read permission here if called from do_execve(). */ > if (current->in_execve) > return 0; > + /* Sockets can't be opened by open(). */ > + if (f->f_path.dentry->d_inode && > + S_ISSOCK(f->f_path.dentry->d_inode->i_mode)) > + return 0; > return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, > f->f_flags); > } > ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] tomoyo: Don't check open/getattr permission on sockets. 2019-06-16 6:49 ` Tetsuo Handa @ 2019-06-18 20:49 ` Al Viro 2019-06-22 4:45 ` [PATCH v2] " Tetsuo Handa 0 siblings, 1 reply; 11+ messages in thread From: Al Viro @ 2019-06-18 20:49 UTC (permalink / raw) To: Tetsuo Handa Cc: linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller On Sun, Jun 16, 2019 at 03:49:00PM +0900, Tetsuo Handa wrote: > Hello, Al. > > Q1: Do you agree that we should fix TOMOYO side rather than SOCKET_I()->sk > management. You do realize that sockets are not unique in that respect, right? All kinds of interesting stuff can be accessed via /proc/*/fd/*, and it _can_ be closed under you. So I'd suggest checking how your code copes with similar for pipes, FIFOs, epoll, etc., accessed that way... We are _not_ going to be checking that in fs/open.c - the stuff found via /proc/*/fd/* can have the associated file closed by the time we get to calling ->open() and we won't know that until said call. > Q2: Do you see any problem with using f->f_path.dentry->d_inode ? > Do we need to use d_backing_inode() or d_inode() ? Huh? What's wrong with file_inode(f), in the first place? And just when can that be NULL, while we are at it? > > static int tomoyo_inode_getattr(const struct path *path) > > { > > + /* It is not safe to call tomoyo_get_socket_name(). */ > > + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) > > + return 0; Can that be called for a negative? ^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-06-18 20:49 ` Al Viro @ 2019-06-22 4:45 ` Tetsuo Handa 2019-08-22 6:30 ` Eric Biggers 0 siblings, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-06-22 4:45 UTC (permalink / raw) To: Al Viro Cc: linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller On 2019/06/19 5:49, Al Viro wrote: > On Sun, Jun 16, 2019 at 03:49:00PM +0900, Tetsuo Handa wrote: >> Hello, Al. >> >> Q1: Do you agree that we should fix TOMOYO side rather than SOCKET_I()->sk >> management. > > You do realize that sockets are not unique in that respect, right? > All kinds of interesting stuff can be accessed via /proc/*/fd/*, and > it _can_ be closed under you. So I'd suggest checking how your code > copes with similar for pipes, FIFOs, epoll, etc., accessed that way... I know all kinds of interesting stuff can be accessed via /proc/*/fd/*, and it _can_ be closed under me. Regarding sockets, I was accessing "struct socket" memory and "struct sock" memory which are outside of "struct inode" memory. But regarding other objects, I am accessing "struct dentry" memory, "struct super_block" memory and "struct inode" memory. I'm expecting that these memory can't be kfree()d as long as "struct path" holds a reference. Is my expectation correct? > > We are _not_ going to be checking that in fs/open.c - the stuff found > via /proc/*/fd/* can have the associated file closed by the time > we get to calling ->open() and we won't know that until said call. OK. Then, fixing TOMOYO side is the correct way. > >> Q2: Do you see any problem with using f->f_path.dentry->d_inode ? >> Do we need to use d_backing_inode() or d_inode() ? > > Huh? What's wrong with file_inode(f), in the first place? And > just when can that be NULL, while we are at it? Oh, I was not aware of file_inode(). Thanks. > >>> static int tomoyo_inode_getattr(const struct path *path) >>> { >>> + /* It is not safe to call tomoyo_get_socket_name(). */ >>> + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) >>> + return 0; > > Can that be called for a negative? > I check for NULL when I'm not sure it is guaranteed to hold a valid pointer. You meant "we are sure that path->dentry->d_inode is valid", don't you? By the way, "negative" associates with IS_ERR() range. I guess that "NULL" is the better name... Anyway, here is V2 patch. From c63c4074300921d6d1c33c3b8dc9c84ebfededf5 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Date: Sat, 22 Jun 2019 13:14:26 +0900 Subject: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. syzbot is reporting that use of SOCKET_I()->sk from open() can result in use after free problem [1], for socket's inode is still reachable via /proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed. But there is no point with calling security_file_open() on sockets because open("/proc/pid/fd/n", !O_PATH) on sockets fails with -ENXIO. There is some point with calling security_inode_getattr() on sockets because stat("/proc/pid/fd/n") and fstat(open("/proc/pid/fd/n", O_PATH)) are valid. If we want to access "struct sock"->sk_{family,type,protocol} fields, we will need to use security_socket_post_create() hook and security_inode_free() hook in order to remember these fields because security_sk_free() hook is called before the inode is destructed. But since information which can be protected by checking security_inode_getattr() on sockets is trivial, let's not be bothered by "struct inode"->i_security management. There is point with calling security_file_ioctl() on sockets. Since ioctl(open("/proc/pid/fd/n", O_PATH)) is invalid, security_file_ioctl() on sockets should remain safe. [1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74 Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com> --- security/tomoyo/tomoyo.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 716c92e..8ea3f5d 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -126,6 +126,9 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) */ static int tomoyo_inode_getattr(const struct path *path) { + /* It is not safe to call tomoyo_get_socket_name(). */ + if (S_ISSOCK(d_inode(path->dentry)->i_mode)) + return 0; return tomoyo_path_perm(TOMOYO_TYPE_GETATTR, path, NULL); } @@ -316,6 +319,9 @@ static int tomoyo_file_open(struct file *f) /* Don't check read permission here if called from do_execve(). */ if (current->in_execve) return 0; + /* Sockets can't be opened by open(). */ + if (S_ISSOCK(file_inode(f)->i_mode)) + return 0; return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, f->f_flags); } -- 1.8.3.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-06-22 4:45 ` [PATCH v2] " Tetsuo Handa @ 2019-08-22 6:30 ` Eric Biggers 2019-08-22 6:55 ` Tetsuo Handa 0 siblings, 1 reply; 11+ messages in thread From: Eric Biggers @ 2019-08-22 6:30 UTC (permalink / raw) To: Tetsuo Handa Cc: Al Viro, linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller Hi Tetsuo, On Sat, Jun 22, 2019 at 01:45:30PM +0900, Tetsuo Handa wrote: > On 2019/06/19 5:49, Al Viro wrote: > > On Sun, Jun 16, 2019 at 03:49:00PM +0900, Tetsuo Handa wrote: > >> Hello, Al. > >> > >> Q1: Do you agree that we should fix TOMOYO side rather than SOCKET_I()->sk > >> management. > > > > You do realize that sockets are not unique in that respect, right? > > All kinds of interesting stuff can be accessed via /proc/*/fd/*, and > > it _can_ be closed under you. So I'd suggest checking how your code > > copes with similar for pipes, FIFOs, epoll, etc., accessed that way... > > I know all kinds of interesting stuff can be accessed via /proc/*/fd/*, > and it _can_ be closed under me. > > Regarding sockets, I was accessing "struct socket" memory and > "struct sock" memory which are outside of "struct inode" memory. > > But regarding other objects, I am accessing "struct dentry" memory, > "struct super_block" memory and "struct inode" memory. I'm expecting > that these memory can't be kfree()d as long as "struct path" holds > a reference. Is my expectation correct? > > > > > We are _not_ going to be checking that in fs/open.c - the stuff found > > via /proc/*/fd/* can have the associated file closed by the time > > we get to calling ->open() and we won't know that until said call. > > OK. Then, fixing TOMOYO side is the correct way. > > > > >> Q2: Do you see any problem with using f->f_path.dentry->d_inode ? > >> Do we need to use d_backing_inode() or d_inode() ? > > > > Huh? What's wrong with file_inode(f), in the first place? And > > just when can that be NULL, while we are at it? > > Oh, I was not aware of file_inode(). Thanks. > > > > >>> static int tomoyo_inode_getattr(const struct path *path) > >>> { > >>> + /* It is not safe to call tomoyo_get_socket_name(). */ > >>> + if (path->dentry->d_inode && S_ISSOCK(path->dentry->d_inode->i_mode)) > >>> + return 0; > > > > Can that be called for a negative? > > > > I check for NULL when I'm not sure it is guaranteed to hold a valid pointer. > You meant "we are sure that path->dentry->d_inode is valid", don't you? > > By the way, "negative" associates with IS_ERR() range. I guess that > "NULL" is the better name... > > Anyway, here is V2 patch. > > From c63c4074300921d6d1c33c3b8dc9c84ebfededf5 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > Date: Sat, 22 Jun 2019 13:14:26 +0900 > Subject: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. > > syzbot is reporting that use of SOCKET_I()->sk from open() can result in > use after free problem [1], for socket's inode is still reachable via > /proc/pid/fd/n despite destruction of SOCKET_I()->sk already completed. > > But there is no point with calling security_file_open() on sockets > because open("/proc/pid/fd/n", !O_PATH) on sockets fails with -ENXIO. > > There is some point with calling security_inode_getattr() on sockets > because stat("/proc/pid/fd/n") and fstat(open("/proc/pid/fd/n", O_PATH)) > are valid. If we want to access "struct sock"->sk_{family,type,protocol} > fields, we will need to use security_socket_post_create() hook and > security_inode_free() hook in order to remember these fields because > security_sk_free() hook is called before the inode is destructed. But > since information which can be protected by checking > security_inode_getattr() on sockets is trivial, let's not be bothered by > "struct inode"->i_security management. > > There is point with calling security_file_ioctl() on sockets. Since > ioctl(open("/proc/pid/fd/n", O_PATH)) is invalid, security_file_ioctl() > on sockets should remain safe. > > [1] https://syzkaller.appspot.com/bug?id=73d590010454403d55164cca23bd0565b1eb3b74 > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > Reported-by: syzbot <syzbot+0341f6a4d729d4e0acf1@syzkaller.appspotmail.com> > --- > security/tomoyo/tomoyo.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c > index 716c92e..8ea3f5d 100644 > --- a/security/tomoyo/tomoyo.c > +++ b/security/tomoyo/tomoyo.c > @@ -126,6 +126,9 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) > */ > static int tomoyo_inode_getattr(const struct path *path) > { > + /* It is not safe to call tomoyo_get_socket_name(). */ > + if (S_ISSOCK(d_inode(path->dentry)->i_mode)) > + return 0; > return tomoyo_path_perm(TOMOYO_TYPE_GETATTR, path, NULL); > } > > @@ -316,6 +319,9 @@ static int tomoyo_file_open(struct file *f) > /* Don't check read permission here if called from do_execve(). */ > if (current->in_execve) > return 0; > + /* Sockets can't be opened by open(). */ > + if (S_ISSOCK(file_inode(f)->i_mode)) > + return 0; > return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, > f->f_flags); > } > -- What happened to this patch? Also, isn't the same bug in other places too?: - tomoyo_path_chmod() - tomoyo_path_chown() - smack_inode_getsecurity() - smack_inode_setsecurity() - Eric ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-08-22 6:30 ` Eric Biggers @ 2019-08-22 6:55 ` Tetsuo Handa 2019-08-22 7:01 ` Eric Biggers 0 siblings, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-08-22 6:55 UTC (permalink / raw) To: Eric Biggers Cc: Al Viro, linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller Eric Biggers wrote: > What happened to this patch? I have to learn how to manage a git tree for sending pull requests, but I can't find time to try. > > Also, isn't the same bug in other places too?: > > - tomoyo_path_chmod() > - tomoyo_path_chown() > - smack_inode_getsecurity() > - smack_inode_setsecurity() What's the bug? The file descriptor returned by open(O_PATH) cannot be passed to read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), mmap(2) etc. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-08-22 6:55 ` Tetsuo Handa @ 2019-08-22 7:01 ` Eric Biggers 2019-08-22 7:42 ` Tetsuo Handa 0 siblings, 1 reply; 11+ messages in thread From: Eric Biggers @ 2019-08-22 7:01 UTC (permalink / raw) To: Tetsuo Handa Cc: Al Viro, linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller On Thu, Aug 22, 2019 at 03:55:31PM +0900, Tetsuo Handa wrote: > Eric Biggers wrote: > > What happened to this patch? > > I have to learn how to manage a git tree for sending > pull requests, but I can't find time to try. > > > > > Also, isn't the same bug in other places too?: > > > > - tomoyo_path_chmod() > > - tomoyo_path_chown() > > - smack_inode_getsecurity() > > - smack_inode_setsecurity() > > What's the bug? The file descriptor returned by open(O_PATH) cannot be > passed to read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), mmap(2) etc. > chmod(2), chown(2), getxattr(2), and setxattr(2) take a path, not a fd. - Eric ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-08-22 7:01 ` Eric Biggers @ 2019-08-22 7:42 ` Tetsuo Handa 2019-08-22 15:47 ` Eric Biggers 0 siblings, 1 reply; 11+ messages in thread From: Tetsuo Handa @ 2019-08-22 7:42 UTC (permalink / raw) To: Eric Biggers Cc: Al Viro, linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller Eric Biggers wrote: > On Thu, Aug 22, 2019 at 03:55:31PM +0900, Tetsuo Handa wrote: > > > Also, isn't the same bug in other places too?: > > > > > > - tomoyo_path_chmod() > > > - tomoyo_path_chown() > > > - smack_inode_getsecurity() > > > - smack_inode_setsecurity() > > > > What's the bug? The file descriptor returned by open(O_PATH) cannot be > > passed to read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), mmap(2) etc. > > > > chmod(2), chown(2), getxattr(2), and setxattr(2) take a path, not a fd. > OK. Then, is the correct fix inode_lock(inode); if (SOCKET_I(inode)->sk) { // Can access SOCKET_I(sock)->sk->* } else { // Already close()d. Don't touch. } inode_unlock(inode); thanks to commit 6d8c50dcb029872b ("socket: close race condition between sock_close() and sockfs_setattr()") commit ff7b11aa481f682e ("net: socket: set sock->sk to NULL after calling proto_ops::release()") changes? ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets. 2019-08-22 7:42 ` Tetsuo Handa @ 2019-08-22 15:47 ` Eric Biggers 0 siblings, 0 replies; 11+ messages in thread From: Eric Biggers @ 2019-08-22 15:47 UTC (permalink / raw) To: Tetsuo Handa Cc: Al Viro, linux-fsdevel, syzbot, jmorris, linux-kernel, linux-security-module, serge, syzkaller-bugs, takedakn, David S. Miller On Thu, Aug 22, 2019 at 04:42:26PM +0900, Tetsuo Handa wrote: > Eric Biggers wrote: > > On Thu, Aug 22, 2019 at 03:55:31PM +0900, Tetsuo Handa wrote: > > > > Also, isn't the same bug in other places too?: > > > > > > > > - tomoyo_path_chmod() > > > > - tomoyo_path_chown() > > > > - smack_inode_getsecurity() > > > > - smack_inode_setsecurity() > > > > > > What's the bug? The file descriptor returned by open(O_PATH) cannot be > > > passed to read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), mmap(2) etc. > > > > > > > chmod(2), chown(2), getxattr(2), and setxattr(2) take a path, not a fd. > > > > OK. Then, is the correct fix > > inode_lock(inode); > if (SOCKET_I(inode)->sk) { > // Can access SOCKET_I(sock)->sk->* > } else { > // Already close()d. Don't touch. > } > inode_unlock(inode); > > thanks to > > commit 6d8c50dcb029872b ("socket: close race condition between sock_close() and sockfs_setattr()") > commit ff7b11aa481f682e ("net: socket: set sock->sk to NULL after calling proto_ops::release()") > > changes? inode_lock() is already held during security_path_chmod(), security_path_chown(), and security_inode_setxattr(). So you can't just take it again. - Eric ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2019-08-22 15:48 UTC | newest] Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- [not found] <0000000000004f43fa058a97f4d3@google.com> 2019-06-06 2:08 ` KASAN: use-after-free Read in tomoyo_realpath_from_path Tetsuo Handa 2019-06-06 5:20 ` Tetsuo Handa 2019-06-09 6:41 ` [PATCH] tomoyo: Don't check open/getattr permission on sockets Tetsuo Handa 2019-06-16 6:49 ` Tetsuo Handa 2019-06-18 20:49 ` Al Viro 2019-06-22 4:45 ` [PATCH v2] " Tetsuo Handa 2019-08-22 6:30 ` Eric Biggers 2019-08-22 6:55 ` Tetsuo Handa 2019-08-22 7:01 ` Eric Biggers 2019-08-22 7:42 ` Tetsuo Handa 2019-08-22 15:47 ` Eric Biggers
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