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authorThomas Weißschuh <linux@weissschuh.net>2024-08-05 11:39:35 +0200
committerJoel Granados <j.granados@samsung.com>2024-09-02 10:37:37 +0200
commit559d4c6a9d3b60f239493239070eb304edaea594 (patch)
tree7f83d15bdcdda2b9b6f76738d12efa49cbe06876 /fs/proc
parent5be63fc19fcaa4c236b307420483578a56986a37 (diff)
sysctl: avoid spurious permanent empty tables
The test if a table is a permanently empty one, inspects the address of the registered ctl_table argument. However as sysctl_mount_point is an empty array and does not occupy and space it can end up sharing an address with another object in memory. If that other object itself is a "struct ctl_table" then registering that table will fail as it's incorrectly recognized as permanently empty. Avoid this issue by adding a dummy element to the array so that is not empty anymore. Explicitly register the table with zero elements as otherwise the dummy element would be recognized as a sentinel element which would lead to a runtime warning from the sysctl core. While the issue seems not being encountered at this time, this seems mostly to be due to luck. Also a future change, constifying sysctl_mount_point and root_table, can reliably trigger this issue on clang 18. Given that empty arrays are non-standard in the first place it seems prudent to avoid them if possible. Fixes: 4a7b29f65094 ("sysctl: move sysctl type to ctl_table_header") Fixes: a35dd3a786f5 ("sysctl: drop now unnecessary out-of-bounds check") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh <linux@weissschuh.net> Closes: https://lore.kernel.org/oe-lkp/202408051453.f638857e-lkp@intel.com Signed-off-by: Joel Granados <j.granados@samsung.com>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/proc_sysctl.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 9553e77c9d31..d11ebc055ce0 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -29,8 +29,13 @@ static const struct inode_operations proc_sys_inode_operations;
static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
-/* Support for permanently empty directories */
-static struct ctl_table sysctl_mount_point[] = { };
+/*
+ * Support for permanently empty directories.
+ * Must be non-empty to avoid sharing an address with other tables.
+ */
+static struct ctl_table sysctl_mount_point[] = {
+ { }
+};
/**
* register_sysctl_mount_point() - registers a sysctl mount point
@@ -42,7 +47,7 @@ static struct ctl_table sysctl_mount_point[] = { };
*/
struct ctl_table_header *register_sysctl_mount_point(const char *path)
{
- return register_sysctl(path, sysctl_mount_point);
+ return register_sysctl_sz(path, sysctl_mount_point, 0);
}
EXPORT_SYMBOL(register_sysctl_mount_point);