Messages in this thread Patch in this message | | | Subject | [PATCH] Reset current->pdeath_signal on SUID binary execution | From | Marcel Holtmann <> | Date | Fri, 17 Aug 2007 21:47:58 +0200 |
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Hi Linus,
the attached patch fixes a flaw in the "parent process death signal" when executing SUID binaries. An unprivileged user may send arbitrary signal to a child process even if it is running with higher privileges.
The idea to fix this issue is to reset pdeath_signal not only on fork, but also on the execution of a SUID binary.
Michael, if we fix it this way, then the prctl() manual page should reflect that behavior.
>From comments it seems that we have to also reset pdeath_signal inside LSM when it comes to capability-raised executes, but I must admit that I got lost there.
Regards
Marcel
[PATCH] Reset current->pdeath_signal on SUID binary execution
This fixes a vulnerability in the "parent process death signal" implementation discoverd by Wojciech Purczynski of COSEINC PTE Ltd. and iSEC Security Research.
http://marc.info/?l=bugtraq&m=118711306802632&w=2
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
--- commit 8542f23e44f591480ca53d215481cbec43b8cbed tree d72f29856adb306f20e828d4bab244685fe24bf2 parent 6adb31c90c47262c8a25bf5097de9b3426caf3ae author Marcel Holtmann <marcel@holtmann.org> Fri, 17 Aug 2007 21:41:52 +0200 committer Marcel Holtmann <marcel@holtmann.org> Fri, 17 Aug 2007 21:41:52 +0200
fs/exec.c | 13 +++++++++---- 1 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c index 7bdea79..ce62f7b 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1084,9 +1084,12 @@ int flush_old_exec(struct linux_binprm * bprm) */ current->mm->task_size = TASK_SIZE; - if (bprm->e_uid != current->euid || bprm->e_gid != current->egid || - file_permission(bprm->file, MAY_READ) || - (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) { + if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) { + suid_keys(current); + set_dumpable(current->mm, suid_dumpable); + current->pdeath_signal = 0; + } else if (file_permission(bprm->file, MAY_READ) || + (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) { suid_keys(current); set_dumpable(current->mm, suid_dumpable); } @@ -1177,8 +1180,10 @@ void compute_creds(struct linux_binprm *bprm) { int unsafe; - if (bprm->e_uid != current->uid) + if (bprm->e_uid != current->uid) { suid_keys(current); + current->pdeath_signal = 0; + } exec_keys(current); task_lock(current); | |