From a30d4ff8193ef768dbb524824c7aa07c5486a63a Mon Sep 17 00:00:00 2001 From: Nir Lichtman Date: Tue, 4 Feb 2025 05:47:41 +0000 Subject: kdb: remove usage of static environment buffer Problem: The set environment variable logic uses a static "heap" like buffer to store the values of the variables, and they are never freed, on top of that this is redundant since the kernel supplies allocation facilities which are even used also in this file. Solution: Remove the weird static buffer logic and use kmalloc instead, call kfree when overriding an existing variable. Signed-off-by: Nir Lichtman Reviewed-by: Douglas Anderson Link: https://lore.kernel.org/r/20250204054741.GB1219827@lichtman.org Signed-off-by: Daniel Thompson --- include/linux/kdb.h | 2 +- kernel/debug/kdb/kdb_main.c | 48 ++++++++------------------------------------- 2 files changed, 9 insertions(+), 41 deletions(-) diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 905a2e2f45f6..ecbf819deeca 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -104,7 +104,7 @@ extern int kdb_initial_cpu; #define KDB_NOENVVALUE (-6) #define KDB_NOTIMP (-7) #define KDB_ENVFULL (-8) -#define KDB_ENVBUFFULL (-9) +#define KDB_KMALLOCFAILED (-9) #define KDB_TOOMANYBPT (-10) #define KDB_TOOMANYDBREGS (-11) #define KDB_DUPBPT (-12) diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 5f4be507d79f..641481b19ada 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -105,7 +105,7 @@ static kdbmsg_t kdbmsgs[] = { KDBMSG(NOENVVALUE, "Environment variable should have value"), KDBMSG(NOTIMP, "Command not implemented"), KDBMSG(ENVFULL, "Environment full"), - KDBMSG(ENVBUFFULL, "Environment buffer full"), + KDBMSG(KMALLOCFAILED, "Failed to allocate memory"), KDBMSG(TOOMANYBPT, "Too many breakpoints defined"), #ifdef CONFIG_CPU_XSCALE KDBMSG(TOOMANYDBREGS, "More breakpoints than ibcr registers defined"), @@ -130,13 +130,9 @@ static const int __nkdb_err = ARRAY_SIZE(kdbmsgs); /* - * Initial environment. This is all kept static and local to - * this file. We don't want to rely on the memory allocation - * mechanisms in the kernel, so we use a very limited allocate-only - * heap for new and altered environment variables. The entire - * environment is limited to a fixed number of entries (add more - * to __env[] if required) and a fixed amount of heap (add more to - * KDB_ENVBUFSIZE if required). + * Initial environment. This is all kept static and local to this file. + * The entire environment is limited to a fixed number of entries + * (add more to __env[] if required) */ static char *__env[31] = { @@ -258,35 +254,6 @@ char *kdbgetenv(const char *match) return NULL; } -/* - * kdballocenv - This function is used to allocate bytes for - * environment entries. - * Parameters: - * bytes The number of bytes to allocate in the static buffer. - * Returns: - * A pointer to the allocated space in the buffer on success. - * NULL if bytes > size available in the envbuffer. - * Remarks: - * We use a static environment buffer (envbuffer) to hold the values - * of dynamically generated environment variables (see kdb_set). Buffer - * space once allocated is never free'd, so over time, the amount of space - * (currently 512 bytes) will be exhausted if env variables are changed - * frequently. - */ -static char *kdballocenv(size_t bytes) -{ -#define KDB_ENVBUFSIZE 512 - static char envbuffer[KDB_ENVBUFSIZE]; - static int envbufsize; - char *ep = NULL; - - if ((KDB_ENVBUFSIZE - envbufsize) >= bytes) { - ep = &envbuffer[envbufsize]; - envbufsize += bytes; - } - return ep; -} - /* * kdbgetulenv - This function will return the value of an unsigned * long-valued environment variable. @@ -348,9 +315,9 @@ static int kdb_setenv(const char *var, const char *val) varlen = strlen(var); vallen = strlen(val); - ep = kdballocenv(varlen + vallen + 2); - if (ep == (char *)0) - return KDB_ENVBUFFULL; + ep = kmalloc(varlen + vallen + 2, GFP_KDB); + if (!ep) + return KDB_KMALLOCFAILED; sprintf(ep, "%s=%s", var, val); @@ -359,6 +326,7 @@ static int kdb_setenv(const char *var, const char *val) && ((strncmp(__env[i], var, varlen) == 0) && ((__env[i][varlen] == '\0') || (__env[i][varlen] == '=')))) { + kfree_const(__env[i]); __env[i] = ep; return 0; } -- cgit v1.2.3 From afdbe49276accb87a0c7414e75864c78289ece2f Mon Sep 17 00:00:00 2001 From: Thorsten Blum Date: Wed, 19 Mar 2025 17:33:39 +0100 Subject: kdb: Remove optional size arguments from strscpy() calls If the destination buffer has a fixed length, strscpy() automatically determines the size of the destination buffer using sizeof() if the argument is omitted. This makes the explicit sizeof() unnecessary. Furthermore, CMD_BUFLEN is equal to sizeof(kdb_prompt_str) and can also be removed. Remove them to shorten and simplify the code. No functional changes intended. Signed-off-by: Thorsten Blum Reviewed-by: Douglas Anderson Reviewed-by: Justin Stitt Link: https://lore.kernel.org/r/20250319163341.2123-2-thorsten.blum@linux.dev Signed-off-by: Daniel Thompson --- kernel/debug/kdb/kdb_io.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 6a77f1c779c4..9b11b10b120c 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -334,7 +334,7 @@ poll_again: *cp = '\0'; p_tmp = strrchr(buffer, ' '); p_tmp = (p_tmp ? p_tmp + 1 : buffer); - strscpy(tmpbuffer, p_tmp, sizeof(tmpbuffer)); + strscpy(tmpbuffer, p_tmp); *cp = tmp; len = strlen(tmpbuffer); @@ -452,7 +452,7 @@ poll_again: char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt) { if (prompt && kdb_prompt_str != prompt) - strscpy(kdb_prompt_str, prompt, CMD_BUFLEN); + strscpy(kdb_prompt_str, prompt); kdb_printf("%s", kdb_prompt_str); kdb_nextline = 1; /* Prompt and input resets line number */ return kdb_read(buffer, bufsize); -- cgit v1.2.3