arm64: idreg-override: Detect trailing "--" in __parse_cmdline()

PATCH In review Thorsten Blum 2 participants 4 messages Oct 15 – Oct 27 arm64

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Thorsten Blum

author

2026-10-15 16:11 UTC #0 lore raw

PATCH 1/1 arm64: idreg-override: Detect trailing "--" in __parse_cmdline()

__parse_cmdline() detects "--" only if it is followed by whitespace. However, at the end of the command line, it converts the dashes to underscores and tries to match "__" as an option.

Detect trailing "--" directly instead of converting it to "__".

Fixes dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")

Signed-off-by Thorsten Blum <[email protected]>

---
 arch/arm64/kernel/pi/idreg-override.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

arch/arm64/kernel/pi/idreg-override.c +3 -2

index acaf56234973..38aa28d19650 100644
@@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 
 		cmdline = skip_spaces(cmdline);
 
-		/* terminate on "--" appearing on the command line by itself */
-		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
+		/* Stop at "--" appearing as a separate argument. */
+		if (cmdline[0] == '-' && cmdline[1] == '-' &&
+		    (!cmdline[2] || isspace(cmdline[2])))
 			return;
 
 		for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {

Catalin Marinas

maintainer

2026-10-27 12:14 UTC #1 lore raw

Quoted 17 lines · Thorsten Blum

__parse_cmdline() detects "--" only if it is followed by whitespace. However, at the end of the command line, it converts the dashes to underscores and tries to match "__" as an option.
Detect trailing "--" directly instead of converting it to "__".
Fixes dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")
Signed-off-by Thorsten Blum <[email protected]>
---
 arch/arm64/kernel/pi/idreg-override.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
arch/arm64/kernel/pi/idreg-override.c +0 -0
index acaf56234973..38aa28d19650 100644

arch/arm64/kernel/pi/idreg-override.c static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) · line 358

Quoted 9 lines

arch/arm64/kernel/pi/idreg-override.c +3 -2

@@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 
 		cmdline = skip_spaces(cmdline);
 
-		/* terminate on "--" appearing on the command line by itself */
-		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
+		/* Stop at "--" appearing as a separate argument. */
+		if (cmdline[0] == '-' && cmdline[1] == '-' &&
+		    (!cmdline[2] || isspace(cmdline[2])))
 			return;

I guess that's more of a cleanup. Does it actually fix anything to deserve a Fixes tag? We skip an unnecessary lookup for "__" but there's no functional difference.

Signature · 1 line

Catalin

Thorsten Blum

author

2026-10-27 14:49 UTC #2 lore raw

Hi Catalin,

Quoted 21 lines · Catalin Marinas

Quoted 20 lines · Thorsten Blum
__parse_cmdline() detects "--" only if it is followed by whitespace. However, at the end of the command line, it converts the dashes to underscores and tries to match "__" as an option.
Detect trailing "--" directly instead of converting it to "__".
Fixes dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")
Signed-off-by Thorsten Blum <[email protected]>
---
 arch/arm64/kernel/pi/idreg-override.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
arch/arm64/kernel/pi/idreg-override.c +0 -0
index acaf56234973..38aa28d19650 100644
@@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 
 		cmdline = skip_spaces(cmdline);
 

Quoted 10 lines

arch/arm64/kernel/pi/idreg-override.c static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) · line 358
Quoted 6 lines
arch/arm64/kernel/pi/idreg-override.c +3 -2
-		/* terminate on "--" appearing on the command line by itself */
-		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
+		/* Stop at "--" appearing as a separate argument. */
+		if (cmdline[0] == '-' && cmdline[1] == '-' &&
+		    (!cmdline[2] || isspace(cmdline[2])))
 			return;
I guess that's more of a cleanup. Does it actually fix anything to deserve a Fixes tag? We skip an unnecessary lookup for "__" but there's no functional difference.

Yes, it's a cleanup.

Functionally, the behavior is equivalent because it also happened to work before. However, commit dc3f5aae0638 removed the explicit detection of a trailing "--", so I added the Fixes tag mostly for provenance.

Thanks,
Thorsten

Catalin Marinas

maintainer Reviewed-by

2026-10-27 16:45 UTC #3 lore raw

Quoted 33 lines · Thorsten Blum

Quoted 21 lines · Catalin Marinas
Quoted 20 lines · Thorsten Blum
__parse_cmdline() detects "--" only if it is followed by whitespace. However, at the end of the command line, it converts the dashes to underscores and tries to match "__" as an option.
Detect trailing "--" directly instead of converting it to "__".
Fixes dc3f5aae0638 ("arm64: idreg-override: Avoid parameq() and parameqn()")
Signed-off-by Thorsten Blum <[email protected]>
---
 arch/arm64/kernel/pi/idreg-override.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
arch/arm64/kernel/pi/idreg-override.c +0 -0
index acaf56234973..38aa28d19650 100644
@@ -352,8 +352,9 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 
 		cmdline = skip_spaces(cmdline);
 
Quoted 10 lines
arch/arm64/kernel/pi/idreg-override.c static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) · line 358
Quoted 6 lines
arch/arm64/kernel/pi/idreg-override.c +3 -2
-		/* terminate on "--" appearing on the command line by itself */
-		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
+		/* Stop at "--" appearing as a separate argument. */
+		if (cmdline[0] == '-' && cmdline[1] == '-' &&
+		    (!cmdline[2] || isspace(cmdline[2])))
 			return;
I guess that's more of a cleanup. Does it actually fix anything to deserve a Fixes tag? We skip an unnecessary lookup for "__" but there's no functional difference.

Quoted 5 lines

Yes, it's a cleanup.
Functionally, the behavior is equivalent because it also happened to work before. However, commit dc3f5aae0638 removed the explicit detection of a trailing "--", so I added the Fixes tag mostly for provenance.

Makes sense. We might make it a comment when applying rather than a dedicated Fixes tag.

Reviewed-by Catalin Marinas <[email protected]>