fs: sysfs_emit_at: Remove PAGE_SIZE alignment check

From: Eric Biggers <[email protected]>

[No upstream commit because this fixes a bug in a backport.]

Before upstream commit 59bb47985c1d ("mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)") which went into v5.4, kmalloc did *not* always guarantee that PAGE_SIZE allocations are PAGE_SIZE-aligned.

Upstream commit 2efc459d06f1 ("sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output") added two WARN()s that trigger when PAGE_SIZE allocations are not PAGE_SIZE-aligned. This was backported to old kernels that don't guarantee PAGE_SIZE alignment.

Commit 10ddfb495232 ("fs: sysfs_emit: Remove PAGE_SIZE alignment check") in 4.19.y, and its equivalent in 4.14.y and 4.9.y, tried to fix this bug. However, only it handled sysfs_emit(), not sysfs_emit_at().

Fix it in sysfs_emit_at() too.

A reproducer is to build the kernel with the following options:

CONFIG_SLUB=y
CONFIG_SLUB_DEBUG=y
CONFIG_SLUB_DEBUG_ON=y
CONFIG_PM=y
CONFIG_SUSPEND=y
CONFIG_PM_WAKELOCKS=y

Then run:

	echo foo > /sys/power/wake_lock && cat /sys/power/wake_lock

---
 fs/sysfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 011e391497f4e..cd70dbeeab226 100644
@@ -599,7 +599,7 @@ int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
 	va_list args;
 	int len;
 
-	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
+	if (WARN(!buf || at < 0 || at >= PAGE_SIZE,
 		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
 		return 0;
 

2.39.2

This is a note to let you know that I've just added the patch titled

fs: sysfs_emit_at: Remove PAGE_SIZE alignment check

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-sysfs_emit_at-remove-page_size-alignment-check.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From [email protected] Fri Mar 17 13:57:17 2023
From: Eric Biggers <[email protected]>
Date: Thu, 16 Mar 2023 23:27:43 -0700
Subject: fs: sysfs_emit_at: Remove PAGE_SIZE alignment check
To: [email protected]
Cc: Joe Perches <[email protected]>, Lucas Wei <[email protected]>, [email protected], kernel test robot <[email protected]>
Message-ID: <[email protected]>

From: Eric Biggers <[email protected]>

From: Eric Biggers <[email protected]>

[No upstream commit because this fixes a bug in a backport.]

Before upstream commit 59bb47985c1d ("mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)") which went into v5.4, kmalloc did *not* always guarantee that PAGE_SIZE allocations are PAGE_SIZE-aligned.

Upstream commit 2efc459d06f1 ("sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output") added two WARN()s that trigger when PAGE_SIZE allocations are not PAGE_SIZE-aligned. This was backported to old kernels that don't guarantee PAGE_SIZE alignment.

Commit 10ddfb495232 ("fs: sysfs_emit: Remove PAGE_SIZE alignment check") in 4.19.y, and its equivalent in 4.14.y and 4.9.y, tried to fix this bug. However, only it handled sysfs_emit(), not sysfs_emit_at().

Fix it in sysfs_emit_at() too.

A reproducer is to build the kernel with the following options:

CONFIG_SLUB=y
CONFIG_SLUB_DEBUG=y
CONFIG_SLUB_DEBUG_ON=y
CONFIG_PM=y
CONFIG_SUSPEND=y
CONFIG_PM_WAKELOCKS=y

Then run:

	echo foo > /sys/power/wake_lock && cat /sys/power/wake_lock

---
 fs/sysfs/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -592,7 +592,7 @@ int sysfs_emit_at(char *buf, int at, con
 	va_list args;
 	int len;
 
-	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
+	if (WARN(!buf || at < 0 || at >= PAGE_SIZE,
 		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
 		return 0;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/fs-sysfs_emit_at-remove-page_size-alignment-check.patch queue-4.14/ext4-fix-cgroup-writeback-accounting-with-fs-layer-encryption.patch

This is a note to let you know that I've just added the patch titled

fs: sysfs_emit_at: Remove PAGE_SIZE alignment check

to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
fs-sysfs_emit_at-remove-page_size-alignment-check.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From [email protected] Fri Mar 17 13:57:17 2023
From: Eric Biggers <[email protected]>
Date: Thu, 16 Mar 2023 23:27:43 -0700
Subject: fs: sysfs_emit_at: Remove PAGE_SIZE alignment check
To: [email protected]
Cc: Joe Perches <[email protected]>, Lucas Wei <[email protected]>, [email protected], kernel test robot <[email protected]>
Message-ID: <[email protected]>

From: Eric Biggers <[email protected]>

From: Eric Biggers <[email protected]>

[No upstream commit because this fixes a bug in a backport.]

Before upstream commit 59bb47985c1d ("mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two)") which went into v5.4, kmalloc did *not* always guarantee that PAGE_SIZE allocations are PAGE_SIZE-aligned.

Upstream commit 2efc459d06f1 ("sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output") added two WARN()s that trigger when PAGE_SIZE allocations are not PAGE_SIZE-aligned. This was backported to old kernels that don't guarantee PAGE_SIZE alignment.

Commit 10ddfb495232 ("fs: sysfs_emit: Remove PAGE_SIZE alignment check") in 4.19.y, and its equivalent in 4.14.y and 4.9.y, tried to fix this bug. However, only it handled sysfs_emit(), not sysfs_emit_at().

Fix it in sysfs_emit_at() too.

A reproducer is to build the kernel with the following options:

CONFIG_SLUB=y
CONFIG_SLUB_DEBUG=y
CONFIG_SLUB_DEBUG_ON=y
CONFIG_PM=y
CONFIG_SUSPEND=y
CONFIG_PM_WAKELOCKS=y

Then run:

	echo foo > /sys/power/wake_lock && cat /sys/power/wake_lock

---
 fs/sysfs/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -599,7 +599,7 @@ int sysfs_emit_at(char *buf, int at, con
 	va_list args;
 	int len;
 
-	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
+	if (WARN(!buf || at < 0 || at >= PAGE_SIZE,
 		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
 		return 0;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.19/fs-sysfs_emit_at-remove-page_size-alignment-check.patch queue-4.19/ext4-fix-cgroup-writeback-accounting-with-fs-layer-encryption.patch