[Crash-utility] Re: [PATCH] “kmem address” not working properly when redzone is enabled

Date: Thu, 29 Aug 2024 09:15:36 +0000 From: "Aureau, Georges (Kernel Tools ERT)" <georges.aureau(a)hpe.com&gt; Subject: [Crash-utility][PATCH] “kmem address” not working properly when redzone is enabled To: &quot;devel(a)lists.crash-utility.osci.io&quot; <devel(a)lists.crash-utility.osci.io&gt; Message-ID: <SJ0PR84MB1482E72F9E168B3B0CE885C89F962(a)SJ0PR84MB1482.NAMP RD84.PROD.OUTLOOK.COM> Content-Type: text/plain; charset="Windows-1252" Crash “kmem address” not working properly when redzone is enabled. When "slub_debug" is enabled with redzoning, "kmem address" does not work properly. The "red_left_pad" member within "struct kmem_cache" is currently an "unsigned int", it used to be an "int", but it never was a "long", hence "red_left_pad" in do_slab_slub() was not initialized properly. This "red_left_pad" issue resulted in reporting free objects as "[ALLOCATED]", and in reporting bogus object addresses when using "set redzone off".

-- diff --git a/memory.c b/memory.c index a74ebaf..967a9cf 100644 --- a/memory.c +++ b/memory.c @@ -19637,7 +19637,8 @@ do_slab_slub(struct meminfo *si, int verbose) int i, free_objects, cpu_slab, is_free, node; ulong p, q; #define SLAB_RED_ZONE 0x00000400UL - ulong flags, red_left_pad; + ulong flags; + uint red_left_pad; if (!si->slab) { if (CRASHDEBUG(1)) @@ -19727,7 +19728,7 @@ do_slab_slub(struct meminfo *si, int verbose) if (VALID_MEMBER(kmem_cache_red_left_pad)) { flags = ULONG(si->cache_buf + OFFSET(kmem_cache_flags)); if (flags & SLAB_RED_ZONE) - red_left_pad = ULONG(si->cache_buf + OFFSET(kmem_cache_red_left_pad)); + red_left_pad = UINT(si->cache_buf + OFFSET(kmem_cache_red_left_pad)); }

for (p = vaddr; p < vaddr + objects * si->size; p += si->size) { ------------------------------