PKGBUILD: Adding bcache_fix.patch to circumenvent bcache related filesystem corruption, when building the kernel with gcc >= 9.0.0.

3 files changed, 135 insertions, 2 deletions

diff --git a/.SRCINFO b/.SRCINFO
index ff0b585..7a88c1a 100644
--- a/.SRCINFO
+++ b/.SRCINFO
@@ -1,6 +1,6 @@
 pkgbase = linux-rt-lts
 	pkgver = 4.19.50_rt22
-	pkgrel = 1
+	pkgrel = 2
 	url = https://git.archlinux.org/linux.git/log/?h=v
 	arch = x86_64
 	license = GPL2
@@ -16,6 +16,7 @@ pkgbase = linux-rt-lts
 	source = https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patch-4.19.50-rt22.patch.xz
 	source = https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patch-4.19.50-rt22.patch.sign
 	source = 0001-add-sysctl-to-disallow-unprivileged-CLONE_NEWUSER-by.patch
+	source = bcache_fix.patch
 	source = config
 	source = 60-linux-rt-lts.hook
 	source = 90-linux-rt-lts.hook
@@ -31,6 +32,7 @@ pkgbase = linux-rt-lts
 	sha256sums = fc842d2e108cd4f21c168de3e3e75f41e43e519dd4dffbc3230bed67e9d24b89
 	sha256sums = SKIP
 	sha256sums = 75aa8dd708ca5a0137fbf7cddc9cafefe6aac6b8e0638c06c156d412d05af4bc
+	sha256sums = fe00e6f26f167b2041f4e60588cc60ab8169f26efb4a7c47ee7d60320e4ca27d
 	sha256sums = 203221ce5e835e55f87585340ca7e50b3a8eefbb58161570479a1cf88963e2b7
 	sha256sums = ae2e95db94ef7176207c690224169594d49445e04249d2499e9d2fbc117a0b21
 	sha256sums = 75f99f5239e03238f88d1a834c50043ec32b1dc568f2cc291b07d04718483919
diff --git a/PKGBUILD b/PKGBUILD
index 0c07dc7..406f255 100644
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -11,7 +11,7 @@ pkgbase=linux-rt-lts       # Build kernel with a different name
 _pkgver=4.19.50
 _rtpatchver=rt22
 pkgver=${_pkgver}_${_rtpatchver}
-pkgrel=1
+pkgrel=2
 arch=('x86_64')
 url="https://git.archlinux.org/linux.git/log/?h=v$_srcver"
 license=('GPL2')
@@ -24,6 +24,7 @@ source=(
   "https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patch-${_pkgver}-${_rtpatchver}.patch.xz"
   "https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patch-${_pkgver}-${_rtpatchver}.patch.sign"
   0001-add-sysctl-to-disallow-unprivileged-CLONE_NEWUSER-by.patch
+  bcache_fix.patch
   config         # the main kernel config file
   60-${pkgbase}.hook  # pacman hook for depmod
   90-${pkgbase}.hook  # pacman hook for initramfs regeneration
@@ -42,6 +43,7 @@ sha256sums=('a9987423918abd20ee68d6e9b14b7225eaca8a586bf75fb56c49f6e1e47ce01e'
             'fc842d2e108cd4f21c168de3e3e75f41e43e519dd4dffbc3230bed67e9d24b89'
             'SKIP'
             '75aa8dd708ca5a0137fbf7cddc9cafefe6aac6b8e0638c06c156d412d05af4bc'
+            'fe00e6f26f167b2041f4e60588cc60ab8169f26efb4a7c47ee7d60320e4ca27d'
             '203221ce5e835e55f87585340ca7e50b3a8eefbb58161570479a1cf88963e2b7'
             'ae2e95db94ef7176207c690224169594d49445e04249d2499e9d2fbc117a0b21'
             '75f99f5239e03238f88d1a834c50043ec32b1dc568f2cc291b07d04718483919'
diff --git a/bcache_fix.patch b/bcache_fix.patch
new file mode 100644
index 0000000..f5c94a5
--- /dev/null
+++ b/bcache_fix.patch
@@ -0,0 +1,129 @@
+From 9e50f5f4ef401c4a5cd286ee3218fcc625ef6f77 Mon Sep 17 00:00:00 2001
+From: Coly Li <colyli@suse.de>
+Date: Mon, 10 Jun 2019 06:13:34 +0800
+Subject: bcache: fix stack corruption by PRECEDING_KEY()
+
+Recently people report bcache code compiled with gcc9 is broken, one of
+the buggy behavior I observe is that two adjacent 4KB I/Os should merge
+into one but they don't. Finally it turns out to be a stack corruption
+caused by macro PRECEDING_KEY().
+
+See how PRECEDING_KEY() is defined in bset.h,
+437 #define PRECEDING_KEY(_k)                                       \
+438 ({                                                              \
+439         struct bkey *_ret = NULL;                               \
+440                                                                 \
+441         if (KEY_INODE(_k) || KEY_OFFSET(_k)) {                  \
+442                 _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);  \
+443                                                                 \
+444                 if (!_ret->low)                                 \
+445                         _ret->high--;                           \
+446                 _ret->low--;                                    \
+447         }                                                       \
+448                                                                 \
+449         _ret;                                                   \
+450 })
+
+At line 442, _ret points to address of a on-stack variable combined by
+KEY(), the life range of this on-stack variable is in line 442-446,
+once _ret is returned to bch_btree_insert_key(), the returned address
+points to an invalid stack address and this address is overwritten in
+the following called bch_btree_iter_init(). Then argument 'search' of
+bch_btree_iter_init() points to some address inside stackframe of
+bch_btree_iter_init(), exact address depends on how the compiler
+allocates stack space. Now the stack is corrupted.
+
+Fixes: 0eacac22034c ("bcache: PRECEDING_KEY()")
+Signed-off-by: Coly Li <colyli@suse.de>
+Reviewed-by: Rolf Fokkens <rolf@rolffokkens.nl>
+Reviewed-by: Pierre JUHEN <pierre.juhen@orange.fr>
+Tested-by: Shenghui Wang <shhuiw@foxmail.com>
+Tested-by: Pierre JUHEN <pierre.juhen@orange.fr>
+Cc: Kent Overstreet <kent.overstreet@gmail.com>
+Cc: Nix <nix@esperi.org.uk>
+Cc: stable@vger.kernel.org
+Signed-off-by: Jens Axboe <axboe@kernel.dk>
+---
+ drivers/md/bcache/bset.c | 16 +++++++++++++---
+ drivers/md/bcache/bset.h | 34 ++++++++++++++++++++--------------
+ 2 files changed, 33 insertions(+), 17 deletions(-)
+
+diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
+index 8f07fa6e1739..268f1b685084 100644
+--- a/drivers/md/bcache/bset.c
++++ b/drivers/md/bcache/bset.c
+@@ -887,12 +887,22 @@ unsigned int bch_btree_insert_key(struct btree_keys *b, struct bkey *k,
+ 	struct bset *i = bset_tree_last(b)->data;
+ 	struct bkey *m, *prev = NULL;
+ 	struct btree_iter iter;
++	struct bkey preceding_key_on_stack = ZERO_KEY;
++	struct bkey *preceding_key_p = &preceding_key_on_stack;
+ 
+ 	BUG_ON(b->ops->is_extents && !KEY_SIZE(k));
+ 
+-	m = bch_btree_iter_init(b, &iter, b->ops->is_extents
+-				? PRECEDING_KEY(&START_KEY(k))
+-				: PRECEDING_KEY(k));
++	/*
++	 * If k has preceding key, preceding_key_p will be set to address
++	 *  of k's preceding key; otherwise preceding_key_p will be set
++	 * to NULL inside preceding_key().
++	 */
++	if (b->ops->is_extents)
++		preceding_key(&START_KEY(k), &preceding_key_p);
++	else
++		preceding_key(k, &preceding_key_p);
++
++	m = bch_btree_iter_init(b, &iter, preceding_key_p);
+ 
+ 	if (b->ops->insert_fixup(b, k, &iter, replace_key))
+ 		return status;
+diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
+index bac76aabca6d..c71365e7c1fa 100644
+--- a/drivers/md/bcache/bset.h
++++ b/drivers/md/bcache/bset.h
+@@ -434,20 +434,26 @@ static inline bool bch_cut_back(const struct bkey *where, struct bkey *k)
+ 	return __bch_cut_back(where, k);
+ }
+ 
+-#define PRECEDING_KEY(_k)					\
+-({								\
+-	struct bkey *_ret = NULL;				\
+-								\
+-	if (KEY_INODE(_k) || KEY_OFFSET(_k)) {			\
+-		_ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);	\
+-								\
+-		if (!_ret->low)					\
+-			_ret->high--;				\
+-		_ret->low--;					\
+-	}							\
+-								\
+-	_ret;							\
+-})
++/*
++ * Pointer '*preceding_key_p' points to a memory object to store preceding
++ * key of k. If the preceding key does not exist, set '*preceding_key_p' to
++ * NULL. So the caller of preceding_key() needs to take care of memory
++ * which '*preceding_key_p' pointed to before calling preceding_key().
++ * Currently the only caller of preceding_key() is bch_btree_insert_key(),
++ * and it points to an on-stack variable, so the memory release is handled
++ * by stackframe itself.
++ */
++static inline void preceding_key(struct bkey *k, struct bkey **preceding_key_p)
++{
++	if (KEY_INODE(k) || KEY_OFFSET(k)) {
++		(**preceding_key_p) = KEY(KEY_INODE(k), KEY_OFFSET(k), 0);
++		if (!(*preceding_key_p)->low)
++			(*preceding_key_p)->high--;
++		(*preceding_key_p)->low--;
++	} else {
++		(*preceding_key_p) = NULL;
++	}
++}
+ 
+ static inline bool bch_ptr_invalid(struct btree_keys *b, const struct bkey *k)
+ {
+-- 
+cgit v1.2.1-1-g437b
+
+