kernel/git/stable/linux.git/fs/exec.c, branch linux-4.17.y

mm: make vm_area_alloc() initialize core fields

2018-08-24T11:07:14+00:00

[ Upstream commit 490fc053865c9cc40f1085ef8a5504f5341f79d2 ] Like vm_area_dup(), it initializes the anon_vma_chain head, and the basic mm pointer. The rest of the fields end up being different for different users, although the plan is to also initialize the 'vm_ops' field to a dummy entry. Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

mm: use helper functions for allocating and freeing vm_area structs

2018-08-24T11:07:14+00:00

[ Upstream commit 3928d4f5ee37cdc523894f6e549e6aae521d8980 ] The vm_area_struct is one of the most fundamental memory management objects, but the management of it is entirely open-coded evertwhere, ranging from allocation and freeing (using kmem_cache_[z]alloc and kmem_cache_free) to initializing all the fields. We want to unify this in order to end up having some unified initialization of the vmas, and the first step to this is to at least have basic allocation functions. Right now those functions are literally just wrappers around the kmem_cache_*() calls. This is a purely mechanical conversion: # new vma: kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL) -> vm_area_alloc() # copy old vma kmem_cache_alloc(vm_area_cachep, GFP_KERNEL) -> vm_area_dup(old) # free vma kmem_cache_free(vm_area_cachep, vma) -> vm_area_free(vma) to the point where the old vma passed in to the vm_area_dup() function isn't even used yet (because I've left all the old manual initialization alone). Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

exec: pin stack limit during exec

2018-04-11T17:28:37+00:00

Since the stack rlimit is used in multiple places during exec and it can be changed via other threads (via setrlimit()) or processes (via prlimit()), the assumption that the value doesn't change cannot be made. This leads to races with mm layout selection and argument size calculations. This changes the exec path to use the rlimit stored in bprm instead of in current. Before starting the thread, the bprm stack rlimit is stored back to current. Link: http://lkml.kernel.org/r/1518638796-20819-4-git-send-email-keescook@chromium.org Fixes: 64701dee4178e ("exec: Use sane stack rlimit under secureexec") Signed-off-by: Kees Cook Reported-by: Ben Hutchings Reported-by: Andy Lutomirski Reported-by: Brad Spengler Acked-by: Michal Hocko Cc: Ben Hutchings Cc: Greg KH Cc: Hugh Dickins Cc: "Jason A. Donenfeld" Cc: Laura Abbott Cc: Oleg Nesterov Cc: Rik van Riel Cc: Willy Tarreau Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exec: introduce finalize_exec() before start_thread()

2018-04-11T17:28:37+00:00

Provide a final callback into fs/exec.c before start_thread() takes over, to handle any last-minute changes, like the coming restoration of the stack limit. Link: http://lkml.kernel.org/r/1518638796-20819-3-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook Cc: Andy Lutomirski Cc: Ben Hutchings Cc: Ben Hutchings Cc: Brad Spengler Cc: Greg KH Cc: Hugh Dickins Cc: "Jason A. Donenfeld" Cc: Laura Abbott Cc: Michal Hocko Cc: Oleg Nesterov Cc: Rik van Riel Cc: Willy Tarreau Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exec: pass stack rlimit into mm layout functions

2018-04-11T17:28:37+00:00

Patch series "exec: Pin stack limit during exec". Attempts to solve problems with the stack limit changing during exec continue to be frustrated[1][2]. In addition to the specific issues around the Stack Clash family of flaws, Andy Lutomirski pointed out[3] other places during exec where the stack limit is used and is assumed to be unchanging. Given the many places it gets used and the fact that it can be manipulated/raced via setrlimit() and prlimit(), I think the only way to handle this is to move away from the "current" view of the stack limit and instead attach it to the bprm, and plumb this down into the functions that need to know the stack limits. This series implements the approach. [1] 04e35f4495dd ("exec: avoid RLIMIT_STACK races with prlimit()") [2] 779f4e1c6c7c ("Revert "exec: avoid RLIMIT_STACK races with prlimit()"") [3] to security@kernel.org, "Subject: existing rlimit races?" This patch (of 3): Since it is possible that the stack rlimit can change externally during exec (either via another thread calling setrlimit() or another process calling prlimit()), provide a way to pass the rlimit down into the per-architecture mm layout functions so that the rlimit can stay in the bprm structure instead of sitting in the signal structure until exec is finalized. Link: http://lkml.kernel.org/r/1518638796-20819-2-git-send-email-keescook@chromium.org Signed-off-by: Kees Cook Cc: Michal Hocko Cc: Ben Hutchings Cc: Willy Tarreau Cc: Hugh Dickins Cc: Oleg Nesterov Cc: "Jason A. Donenfeld" Cc: Rik van Riel Cc: Laura Abbott Cc: Greg KH Cc: Andy Lutomirski Cc: Ben Hutchings Cc: Brad Spengler Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exec: Set file unwritable before LSM check

2018-03-19T04:49:32+00:00

The LSM check should happen after the file has been confirmed to be unchanging. Without this, we could have a race between the Time of Check (the call to security_kernel_read_file() which could read the file and make access policy decisions) and the Time of Use (starting with kernel_read_file()'s reading of the file contents). In theory, file contents could change between the two. Signed-off-by: Kees Cook Reviewed-by: Mimi Zohar Signed-off-by: James Morris

exec: Weaken dumpability for secureexec

2018-01-03T18:13:36+00:00

This is a logical revert of commit e37fdb785a5f ("exec: Use secureexec for setting dumpability") This weakens dumpability back to checking only for uid/gid changes in current (which is useless), but userspace depends on dumpability not being tied to secureexec. https://bugzilla.redhat.com/show_bug.cgi?id=1528633 Reported-by: Tom Horsley Fixes: e37fdb785a5f ("exec: Use secureexec for setting dumpability") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds

Revert "exec: avoid RLIMIT_STACK races with prlimit()"

2017-12-17T22:26:25+00:00

This reverts commit 04e35f4495dd560db30c25efca4eecae8ec8c375. SELinux runs with secureexec for all non-"noatsecure" domain transitions, which means lots of processes end up hitting the stack hard-limit change that was introduced in order to fix a race with prlimit(). That race fix will need to be redesigned. Reported-by: Laura Abbott Reported-by: Tomáš Trnka Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds

exec: avoid gcc-8 warning for get_task_comm

2017-12-15T00:00:48+00:00

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

exec: avoid RLIMIT_STACK races with prlimit()

2017-11-30T02:40:42+00:00

While the defense-in-depth RLIMIT_STACK limit on setuid processes was protected against races from other threads calling setrlimit(), I missed protecting it against races from external processes calling prlimit(). This adds locking around the change and makes sure that rlim_max is set too. Link: http://lkml.kernel.org/r/20171127193457.GA11348@beast Fixes: 64701dee4178e ("exec: Use sane stack rlimit under secureexec") Signed-off-by: Kees Cook Reported-by: Ben Hutchings Reported-by: Brad Spengler Acked-by: Serge Hallyn Cc: James Morris Cc: Andy Lutomirski Cc: Oleg Nesterov Cc: Jiri Slaby Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds