user/sven/linux.git/fs/exec.c, branch v4.9.287

exit/exec: Seperate mm_release()

2021-02-03T22:19:49Z

commit 4610ba7ad877fafc0a25a30c6c82015304120426 upstream. mm_release() contains the futex exit handling. mm_release() is called from do_exit()->exit_mm() and from exec()->exec_mm(). In the exit_mm() case PF_EXITING and the futex state is updated. In the exec_mm() case these states are not touched. As the futex exit code needs further protections against exit races, this needs to be split into two functions. Preparatory only, no functional change. Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20191106224556.240518241@linutronix.de Signed-off-by: Greg Kroah-Hartman Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

exec: Move would_dump into flush_old_exec

2020-05-20T06:15:41Z

commit f87d1c9559164294040e58f5e3b74a162bf7c6e8 upstream. I goofed when I added mm->user_ns support to would_dump. I missed the fact that in the case of binfmt_loader, binfmt_em86, binfmt_misc, and binfmt_script bprm->file is reassigned. Which made the move of would_dump from setup_new_exec to __do_execve_file before exec_binprm incorrect as it can result in would_dump running on the script instead of the interpreter of the script. The net result is that the code stopped making unreadable interpreters undumpable. Which allows them to be ptraced and written to disk without special permissions. Oops. The move was necessary because the call in set_new_exec was after bprm->mm was no longer valid. To correct this mistake move the misplaced would_dump from __do_execve_file into flos_old_exec, before exec_mmap is called. I tested and confirmed that without this fix I can attach with gdb to a script with an unreadable interpreter, and with this fix I can not. Cc: stable@vger.kernel.org Fixes: f84df2a6f268 ("exec: Ensure mm->user_ns contains the execed files") Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

signal: Extend exec_id to 64bits

2020-04-24T05:58:54Z

commit d1e7fd6462ca9fc76650fbe6ca800e35b24267da upstream. Replace the 32bit exec_id with a 64bit exec_id to make it impossible to wrap the exec_id counter. With care an attacker can cause exec_id wrap and send arbitrary signals to a newly exec'd parent. This bypasses the signal sending checks if the parent changes their credentials during exec. The severity of this problem can been seen that in my limited testing of a 32bit exec_id it can take as little as 19s to exec 65536 times. Which means that it can take as little as 14 days to wrap a 32bit exec_id. Adam Zabrocki has succeeded wrapping the self_exe_id in 7 days. Even my slower timing is in the uptime of a typical server. Which means self_exec_id is simply a speed bump today, and if exec gets noticably faster self_exec_id won't even be a speed bump. Extending self_exec_id to 64bits introduces a problem on 32bit architectures where reading self_exec_id is no longer atomic and can take two read instructions. Which means that is is possible to hit a window where the read value of exec_id does not match the written value. So with very lucky timing after this change this still remains expoiltable. I have updated the update of exec_id on exec to use WRITE_ONCE and the read of exec_id in do_notify_parent to use READ_ONCE to make it clear that there is no locking between these two locations. Link: https://lore.kernel.org/kernel-hardening/20200324215049.GA3710@pi3.com.pl Fixes: 2.3.23pre2 Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

sched/fair: Don't free p->numa_faults with concurrent readers

2019-08-04T07:33:45Z

commit 16d51a590a8ce3befb1308e0e7ab77f3b661af33 upstream. When going through execve(), zero out the NUMA fault statistics instead of freeing them. During execve, the task is reachable through procfs and the scheduler. A concurrent /proc/*/sched reader can read data from a freed ->numa_faults allocation (confirmed by KASAN) and write it back to userspace. I believe that it would also be possible for a use-after-free read to occur through a race between a NUMA fault and execve(): task_numa_fault() can lead to task_numa_compare(), which invokes task_weight() on the currently running task of a different CPU. Another way to fix this would be to make ->numa_faults RCU-managed or add extra locking, but it seems easier to wipe the NUMA fault statistics on execve. Signed-off-by: Jann Horn Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Thomas Gleixner Cc: Will Deacon Fixes: 82727018b0d3 ("sched/numa: Call task_numa_free() from do_execve()") Link: https://lkml.kernel.org/r/20190716152047.14424-1-jannh@google.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

exec: Fix mem leak in kernel_read_file

2019-03-13T21:04:55Z

commit f612acfae86af7ecad754ae6a46019be9da05b8e upstream. syzkaller report this: BUG: memory leak unreferenced object 0xffffc9000488d000 (size 9195520): comm "syz-executor.0", pid 2752, jiffies 4294787496 (age 18.757s) hex dump (first 32 bytes): ff ff ff ff ff ff ff ff a8 00 00 00 01 00 00 00 ................ 02 00 00 00 00 00 00 00 80 a1 7a c1 ff ff ff ff ..........z..... backtrace: [<000000000863775c>] __vmalloc_node mm/vmalloc.c:1795 [inline] [<000000000863775c>] __vmalloc_node_flags mm/vmalloc.c:1809 [inline] [<000000000863775c>] vmalloc+0x8c/0xb0 mm/vmalloc.c:1831 [<000000003f668111>] kernel_read_file+0x58f/0x7d0 fs/exec.c:924 [<000000002385813f>] kernel_read_file_from_fd+0x49/0x80 fs/exec.c:993 [<0000000011953ff1>] __do_sys_finit_module+0x13b/0x2a0 kernel/module.c:3895 [<000000006f58491f>] do_syscall_64+0x147/0x600 arch/x86/entry/common.c:290 [<00000000ee78baf4>] entry_SYSCALL_64_after_hwframe+0x49/0xbe [<00000000241f889b>] 0xffffffffffffffff It should goto 'out_free' lable to free allocated buf while kernel_read fails. Fixes: 39d637af5aa7 ("vfs: forbid write access when reading a file into memory") Signed-off-by: YueHaibing Signed-off-by: Al Viro Cc: Thibaut Sautereau Signed-off-by: Greg Kroah-Hartman

exec: avoid gcc-8 warning for get_task_comm

2018-07-28T05:49:14Z

commit 3756f6401c302617c5e091081ca4d26ab604bec5 upstream. gcc-8 warns about using strncpy() with the source size as the limit: fs/exec.c:1223:32: error: argument to 'sizeof' in 'strncpy' call is the same expression as the source; did you mean to use the size of the destination? [-Werror=sizeof-pointer-memaccess] This is indeed slightly suspicious, as it protects us from source arguments without NUL-termination, but does not guarantee that the destination is terminated. This keeps the strncpy() to ensure we have properly padded target buffer, but ensures that we use the correct length, by passing the actual length of the destination buffer as well as adding a build-time check to ensure it is exactly TASK_COMM_LEN. There are only 23 callsites which I all reviewed to ensure this is currently the case. We could get away with doing only the check or passing the right length, but it doesn't hurt to do both. Link: http://lkml.kernel.org/r/20171205151724.1764896-1-arnd@arndb.de Signed-off-by: Arnd Bergmann Suggested-by: Kees Cook Acked-by: Kees Cook Acked-by: Ingo Molnar Cc: Alexander Viro Cc: Peter Zijlstra Cc: Serge Hallyn Cc: James Morris Cc: Aleksa Sarai Cc: "Eric W. Biederman" Cc: Frederic Weisbecker Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

exec: Limit arg stack to at most 75% of _STK_LIM

2017-07-21T05:42:22Z

commit da029c11e6b12f321f36dac8771e833b65cec962 upstream. To avoid pathological stack usage or the need to special-case setuid execs, just limit all arg stack usage to at most 75% of _STK_LIM (6MB). Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

fs/exec.c: account for argv/envp pointers

2017-06-29T11:00:28Z

commit 98da7d08850fb8bdeb395d6368ed15753304aa0c upstream. When limiting the argv/envp strings during exec to 1/4 of the stack limit, the storage of the pointers to the strings was not included. This means that an exec with huge numbers of tiny strings could eat 1/4 of the stack limit in strings and then additional space would be later used by the pointers to the strings. For example, on 32-bit with a 8MB stack rlimit, an exec with 1677721 single-byte strings would consume less than 2MB of stack, the max (8MB / 4) amount allowed, but the pointers to the strings would consume the remaining additional stack space (1677721 * 4 == 6710884). The result (1677721 + 6710884 == 8388605) would exhaust stack space entirely. Controlling this stack exhaustion could result in pathological behavior in setuid binaries (CVE-2017-1000365). [akpm@linux-foundation.org: additional commenting from Kees] Fixes: b6a2fea39318 ("mm: variable length argument support") Link: http://lkml.kernel.org/r/20170622001720.GA32173@beast Signed-off-by: Kees Cook Acked-by: Rik van Riel Acked-by: Michal Hocko Cc: Alexander Viro Cc: Qualys Security Advisory Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

ptrace: Capture the ptracer's creds not PT_PTRACE_CAP

2017-01-06T09:40:13Z

commit 64b875f7ac8a5d60a4e191479299e931ee949b67 upstream. When the flag PT_PTRACE_CAP was added the PTRACE_TRACEME path was overlooked. This can result in incorrect behavior when an application like strace traces an exec of a setuid executable. Further PT_PTRACE_CAP does not have enough information for making good security decisions as it does not report which user namespace the capability is in. This has already allowed one mistake through insufficient granulariy. I found this issue when I was testing another corner case of exec and discovered that I could not get strace to set PT_PTRACE_CAP even when running strace as root with a full set of caps. This change fixes the above issue with strace allowing stracing as root a setuid executable without disabling setuid. More fundamentaly this change allows what is allowable at all times, by using the correct information in it's decision. Fixes: 4214e42f96d4 ("v2.4.9.11 -> v2.4.9.12") Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

fs: exec: apply CLOEXEC before changing dumpable task flags

2017-01-06T09:40:12Z

commit 613cc2b6f272c1a8ad33aefa21cad77af23139f7 upstream. If you have a process that has set itself to be non-dumpable, and it then undergoes exec(2), any CLOEXEC file descriptors it has open are "exposed" during a race window between the dumpable flags of the process being reset for exec(2) and CLOEXEC being applied to the file descriptors. This can be exploited by a process by attempting to access /proc//fd/... during this window, without requiring CAP_SYS_PTRACE. The race in question is after set_dumpable has been (for get_link, though the trace is basically the same for readlink): [vfs] -> proc_pid_link_inode_operations.get_link -> proc_pid_get_link -> proc_fd_access_allowed -> ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); Which will return 0, during the race window and CLOEXEC file descriptors will still be open during this window because do_close_on_exec has not been called yet. As a result, the ordering of these calls should be reversed to avoid this race window. This is of particular concern to container runtimes, where joining a PID namespace with file descriptors referring to the host filesystem can result in security issues (since PRCTL_SET_DUMPABLE doesn't protect against access of CLOEXEC file descriptors -- file descriptors which may reference filesystem objects the container shouldn't have access to). Cc: dev@opencontainers.org Reported-by: Michael Crosby Signed-off-by: Aleksa Sarai Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman