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authorRafael Aquini <aquini@redhat.com>2020-06-07 21:40:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-08 11:05:56 -0700
commitdb38d5c106dfdd7cb7207c83267d82fdf4950b61 (patch)
tree1b6d4b08878942fb32dcd6b2faccfd7cf32babb2 /kernel/sysctl.c
parentceabef7dd71720aef58bd182943352c9c307a3de (diff)
kernel: add panic_on_taint
Analogously to the introduction of panic_on_warn, this patch introduces a kernel option named panic_on_taint in order to provide a simple and generic way to stop execution and catch a coredump when the kernel gets tainted by any given flag. This is useful for debugging sessions as it avoids having to rebuild the kernel to explicitly add calls to panic() into the code sites that introduce the taint flags of interest. For instance, if one is interested in proceeding with a post-mortem analysis at the point a given code path is hitting a bad page (i.e. unaccount_page_cache_page(), or slab_bug()), a coredump can be collected by rebooting the kernel with 'panic_on_taint=0x20' amended to the command line. Another, perhaps less frequent, use for this option would be as a means for assuring a security policy case where only a subset of taints, or no single taint (in paranoid mode), is allowed for the running system. The optional switch 'nousertaint' is handy in this particular scenario, as it will avoid userspace induced crashes by writes to sysctl interface /proc/sys/kernel/tainted causing false positive hits for such policies. [akpm@linux-foundation.org: tweak kernel-parameters.txt wording] Suggested-by: Qian Cai <cai@lca.pw> Signed-off-by: Rafael Aquini <aquini@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Dave Young <dyoung@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kees Cook <keescook@chromium.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Adrian Bunk <bunk@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Laura Abbott <labbott@redhat.com> Cc: Jeff Mahoney <jeffm@suse.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Takashi Iwai <tiwai@suse.de> Link: http://lkml.kernel.org/r/20200515175502.146720-1-aquini@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
-rw-r--r--kernel/sysctl.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 715774d8c55f..587ed0494f2f 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -866,11 +866,20 @@ static int proc_taint(struct ctl_table *table, int write,
return err;
if (write) {
+ int i;
+
+ /*
+ * If we are relying on panic_on_taint not producing
+ * false positives due to userspace input, bail out
+ * before setting the requested taint flags.
+ */
+ if (panic_on_taint_nousertaint && (tmptaint & panic_on_taint))
+ return -EINVAL;
+
/*
* Poor man's atomic or. Not worth adding a primitive
* to everyone's atomic.h for this
*/
- int i;
for (i = 0; i < BITS_PER_LONG && tmptaint >> i; i++) {
if ((tmptaint >> i) & 1)
add_taint(i, LOCKDEP_STILL_OK);