codetag_needs_module_section() is called twice per codetag section, once
in layout_sections() and once in move_module(), and both depend on
mem_profiling_support, which changes without a lock. If profiling is
disabled between the two calls, layout excludes the section (offset 0)
while move copies it as normal memory to offset 0:
CPU0 (insmod A) CPU1 (insmod B)
---------------- ----------------
layout_sections()
needs_section_mem() == true
sh_entsize: type, offset = 0
reserve_module_tags() overflows
shutdown_mem_profiling()
mem_profiling_support = false
move_module()
needs_section_mem() == false
offset = sh_entsize & MASK = 0
memcpy(mod->mem[type].base + 0, ...)
-> overwrites the first section there
Record the decision in layout_sections() in sh_entsize using a
MOD_MEM_CODETAG type, and have move_module() use that instead of asking
again.
reserve_module_tags() returns -EAGAIN if profiling was disabled after
layout, so the loader retries and places the section as normal memory.
Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression")
Signed-off-by: Hao Ge <[email protected]>
---
include/linux/module.h | 11 +++++++++++
kernel/module/main.c | 17 ++++++-----------
mm/alloc_tag.c | 8 ++++++++
3 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index 7566815fabbe..a02016528e1d 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -328,6 +328,17 @@ enum mod_mem_type {
MOD_INVALID = -1,
};
+/*
+ * If CONFIG_CODE_TAGGING is on, modules get a .codetag section.
+ * codetag_needs_module_section() says where it goes: the usual
+ * mod->mem[], or off to the codetag region.
+ *
+ * Mark the codetag-region ones with MOD_MEM_NUM_TYPES.
+ * It's just past the real types, so it doesn't index into mod->mem[]
+ * and for_each_mod_mem_type() skips it.
+ */
+#define MOD_MEM_CODETAG MOD_MEM_NUM_TYPES
+
#define mod_mem_type_is_init(type) \
((type) == MOD_INIT_TEXT || \
(type) == MOD_INIT_DATA || \
diff --git a/kernel/module/main.c b/kernel/module/main.c
index ed26f167be84..2337bf604f58 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1728,11 +1728,8 @@ static void __layout_sections(struct module *mod, struct
load_info *info, bool i
* preallocated contiguous memory.
*/
if (codetag_needs_module_section(mod, sname,
s->sh_size)) {
- /*
- * s->sh_entsize won't be used but populate the
- * type field to avoid confusion.
- */
- s->sh_entsize = ((unsigned long)(type) &
SH_ENTSIZE_TYPE_MASK)
+ s->sh_entsize = ((unsigned long)MOD_MEM_CODETAG
+ & SH_ENTSIZE_TYPE_MASK)
<< SH_ENTSIZE_TYPE_SHIFT;
continue;
}
@@ -2815,11 +2812,10 @@ static int move_module(struct module *mod, struct
load_info *info)
continue;
sname = info->secstrings + shdr->sh_name;
- /*
- * Load codetag sections separately as they might still be used
- * after module unload.
- */
- if (codetag_needs_module_section(mod, sname, shdr->sh_size)) {
+
+ enum mod_mem_type type = shdr->sh_entsize >>
SH_ENTSIZE_TYPE_SHIFT;
+
+ if (type == MOD_MEM_CODETAG) {
dest = codetag_alloc_module_section(mod, sname,
shdr->sh_size,
arch_mod_section_prepend(mod, i),
shdr->sh_addralign);
if (WARN_ON(!dest)) {
@@ -2832,7 +2828,6 @@ static int move_module(struct module *mod, struct
load_info *info)
}
codetag_section_found = true;
} else {
- enum mod_mem_type type = shdr->sh_entsize >>
SH_ENTSIZE_TYPE_SHIFT;
unsigned long offset = shdr->sh_entsize &
SH_ENTSIZE_OFFSET_MASK;
dest = mod->mem[type].base + offset;
diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c
index 461fa87fbb0b..7481180dadd2 100644
--- a/mm/alloc_tag.c
+++ b/mm/alloc_tag.c
@@ -893,6 +893,14 @@ static void *reserve_module_tags(struct module *mod,
unsigned long size,
if (size < sizeof(struct alloc_tag))
return ERR_PTR(-EINVAL);
+ /*
+ * Profiling may have been disabled by a concurrent module load.
+ * Return -EAGAIN so the loader retries with profiling off, laying
+ * the section out as ordinary module memory.
+ */
+ if (!mem_profiling_support)
+ return ERR_PTR(-EAGAIN);
+
/*
* align is always power of 2, so we can use IS_ALIGNED and ALIGN.
* align 0 or 1 means no alignment, to simplify set to 1.
--
2.25.1
