pstore: Change kmsg_bytes storage size to u32

The types around kmsg_bytes were inconsistent. The global was unsigned
long, the argument to pstore_set_kmsg_bytes() was int, and the filesystem
option was u32. Given other internal limits, there's not much sense
in making a single pstore record larger than INT_MAX and it can't be
negative, so use u32 everywhere. Additionally, use READ/WRITE_ONCE and a
local variable in pstore_dump() to avoid kmsg_bytes changing during a
dump.

Link: https://lore.kernel.org/r/20250206191655.work.798-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 56815799ce798ef0eee28f92518e6ed39a24081c..9de6b280c4f411c25b13d9bbf5667f53ef796372 100644 (file)
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -265,7 +265,7 @@ static void parse_options(char *options)
 static int pstore_show_options(struct seq_file *m, struct dentry *root)
 {
        if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
-               seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
+               seq_printf(m, ",kmsg_bytes=%u", kmsg_bytes);
        return 0;
 }
 

diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index 801d6c0b170c3aaee647ad9fd1f536ae03de331a..a0fc511969100ca8d6024489e3e537ce7c68f6f0 100644 (file)
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -6,7 +6,7 @@
 #include <linux/time.h>
 #include <linux/pstore.h>
 
-extern unsigned long kmsg_bytes;
+extern unsigned int kmsg_bytes;
 
 #ifdef CONFIG_PSTORE_FTRACE
 extern void pstore_register_ftrace(void);
@@ -35,7 +35,7 @@ static inline void pstore_unregister_pmsg(void) {}
 
 extern struct pstore_info *psinfo;
 
-extern void    pstore_set_kmsg_bytes(int);
+extern void    pstore_set_kmsg_bytes(unsigned int bytes);
 extern void    pstore_get_records(int);
 extern void    pstore_get_backend_records(struct pstore_info *psi,
                                           struct dentry *root, int quiet);

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index f56b066ab80ce4ef95f6822e32aa42942c1a9768..557cf9d40177f6d01b466c823bdca41a227d749f 100644 (file)
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -92,8 +92,8 @@ module_param(compress, charp, 0444);
 MODULE_PARM_DESC(compress, "compression to use");
 
 /* How much of the kernel log to snapshot */
-unsigned long kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
-module_param(kmsg_bytes, ulong, 0444);
+unsigned int kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
+module_param(kmsg_bytes, uint, 0444);
 MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)");
 
 static void *compress_workspace;
@@ -107,9 +107,9 @@ static void *compress_workspace;
 static char *big_oops_buf;
 static size_t max_compressed_size;
 
-void pstore_set_kmsg_bytes(int bytes)
+void pstore_set_kmsg_bytes(unsigned int bytes)
 {
-       kmsg_bytes = bytes;
+       WRITE_ONCE(kmsg_bytes, bytes);
 }
 
 /* Tag each group of saved records with a sequence number */
@@ -278,6 +278,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
                        struct kmsg_dump_detail *detail)
 {
        struct kmsg_dump_iter iter;
+       unsigned int    remaining = READ_ONCE(kmsg_bytes);
        unsigned long   total = 0;
        const char      *why;
        unsigned int    part = 1;
@@ -300,7 +301,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
        kmsg_dump_rewind(&iter);
 
        oopscount++;
-       while (total < kmsg_bytes) {
+       while (total < remaining) {
                char *dst;
                size_t dst_size;
                int header_size;