The patch titled binfmt_misc.c: avoid potential kernel stack overflow has been added to the -mm tree. Its filename is binfmt_miscc-avoid-potential-kernel-stack-overflow.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: binfmt_misc.c: avoid potential kernel stack overflow From: Pavel Emelyanov <xemul@xxxxxxxxxx> This can be triggered with root help only, but... Register the ":text:E::txt::/root/cat.txt:' rule in binfmt_misc (by root) and try launching the cat.txt file (by anyone) :) The result is - the endless recursion in the load_misc_binary -> open_exec -> load_misc_binary chain and stack overflow. There's a similar problem with binfmt_script, and there's a sh_bang memner on linux_binprm structure to handle this, but simply raising this in binfmt_misc may break some setups when the interpreter of some misc binaries is a script. So the proposal is to turn sh_bang into a bit, add a new one (the misc_bang) and raise it in load_misc_binary. After this, even if we set up the misc -> script -> misc loop for binfmts one of them will step on its own bang and exit. Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/binfmt_em86.c | 2 +- fs/binfmt_misc.c | 6 ++++++ fs/binfmt_script.c | 2 +- include/linux/binfmts.h | 3 ++- 4 files changed, 10 insertions(+), 3 deletions(-) diff -puN fs/binfmt_em86.c~binfmt_miscc-avoid-potential-kernel-stack-overflow fs/binfmt_em86.c --- a/fs/binfmt_em86.c~binfmt_miscc-avoid-potential-kernel-stack-overflow +++ a/fs/binfmt_em86.c @@ -43,7 +43,7 @@ static int load_em86(struct linux_binprm return -ENOEXEC; } - bprm->sh_bang++; /* Well, the bang-shell is implicit... */ + bprm->sh_bang = 1; /* Well, the bang-shell is implicit... */ allow_write_access(bprm->file); fput(bprm->file); bprm->file = NULL; diff -puN fs/binfmt_misc.c~binfmt_miscc-avoid-potential-kernel-stack-overflow fs/binfmt_misc.c --- a/fs/binfmt_misc.c~binfmt_miscc-avoid-potential-kernel-stack-overflow +++ a/fs/binfmt_misc.c @@ -116,6 +116,12 @@ static int load_misc_binary(struct linux if (!enabled) goto _ret; + retval = -ENOEXEC; + if (bprm->misc_bang) + goto _ret; + + bprm->misc_bang = 1; + /* to keep locking time low, we copy the interpreter string */ read_lock(&entries_lock); fmt = check_file(bprm); diff -puN fs/binfmt_script.c~binfmt_miscc-avoid-potential-kernel-stack-overflow fs/binfmt_script.c --- a/fs/binfmt_script.c~binfmt_miscc-avoid-potential-kernel-stack-overflow +++ a/fs/binfmt_script.c @@ -29,7 +29,7 @@ static int load_script(struct linux_binp * Sorta complicated, but hopefully it will work. -TYT */ - bprm->sh_bang++; + bprm->sh_bang = 1; allow_write_access(bprm->file); fput(bprm->file); bprm->file = NULL; diff -puN include/linux/binfmts.h~binfmt_miscc-avoid-potential-kernel-stack-overflow include/linux/binfmts.h --- a/include/linux/binfmts.h~binfmt_miscc-avoid-potential-kernel-stack-overflow +++ a/include/linux/binfmts.h @@ -34,7 +34,8 @@ struct linux_binprm{ #endif struct mm_struct *mm; unsigned long p; /* current top of mem */ - int sh_bang; + unsigned int sh_bang:1, + misc_bang:1; struct file * file; int e_uid, e_gid; kernel_cap_t cap_inheritable, cap_permitted; _ Patches currently in -mm which might be from xemul@xxxxxxxxxx are origin.patch git-kgdb-light.patch use-find_task_by_vpid-in-audit-code.patch ia64-fix-getpid-and-set_tid_address-fast-system-calls-for-pid-namespaces.patch git-udf.patch mm-have-zonelist-contains-structs-with-both-a-zone-pointer-and-zone_idx-fix-memcg-ooms.patch mm-have-zonelist-contains-structs-with-both-a-zone-pointer-and-zone_idx-just-return-do_try_to_free_pages.patch mm-have-zonelist-contains-structs-with-both-a-zone-pointer-and-zone_idx-just-return-do_try_to_free_pages-do_try_to_free_pages-gfp_mask-redundant.patch binfmt_miscc-avoid-potential-kernel-stack-overflow.patch cgroup-api-files-rename-read-write_uint-methods-to-read_write_u64.patch cgroup-api-files-add-res_counter_read_u64.patch cgroup-api-files-use-read_u64-in-memory-controller.patch cgroup-api-files-strip-all-trailing-whitespace-in-cgroup_write_u64.patch cgroup-api-files-update-cpusets-to-use-cgroup-structured-file-api.patch cgroup-api-files-update-cpusets-to-use-cgroup-structured-file-api-fix.patch cgroup-api-files-add-cgroup-map-data-type.patch cgroup-api-files-use-cgroup-map-for-memcontrol-stats-file.patch cgroup-api-files-drop-mem_cgroup_force_empty.patch cgroup-api-files-move-releasable-to-cgroup_debug-subsystem.patch cgroup-api-files-make-cgroup_debug-default-to-off.patch cgroups-add-cgroup-support-for-enabling-controllers-at-boot-time.patch memory-controller-make-memory-resource-control-aware-of-boot-options.patch memcgroup-add-the-max_usage-member-on-the-res_counter.patch add-a-document-describing-the-resource-counter-abstraction-v2.patch memcgroup-move-memory-controller-allocations-to-their-own-slabs.patch remove-unused-variable-from-send_signal.patch turn-legacy_queue-macro-into-static-inline-function.patch consolidate-checking-for-ignored-legacy-signals.patch consolidate-checking-for-ignored-legacy-signals-simplify.patch signals-consolidate-checks-for-whether-or-not-to-ignore-a-signal.patch signals-clean-dequeue_signal-from-excess-checks-and-assignments.patch signals-consolidate-send_sigqueue-and-send_group_sigqueue.patch signals-cleanup-security_task_kill-usage-implementation.patch signals-use-__group_complete_signal-for-the-specific-signals-too.patch signals-fold-complete_signal-into-send_signal-do_send_sigqueue.patch signals-unify-send_sigqueue-send_group_sigqueue-completely.patch sysctl-merge-equal-proc_sys_read-and-proc_sys_write.patch sysctl-clean-from-unneeded-extern-and-forward-declarations.patch sysctl-add-the-permissions-callback-on-the-ctl_table_root.patch free_pidmap-turn-it-into-free_pidmapstruct-upid.patch use-find_task_by_vpid-in-taskstats.patch deprecate-find_task_by_pid.patch deprecate-find_task_by_pid-warning-fix.patch pidns-make-pid-level-and-pid_ns-level-unsigned.patch reiser4.patch put_pid-make-sure-we-dont-free-the-live-pid.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html