From 82d12088c297fa1cef670e1718b3d24f414c23f7 Mon Sep 17 00:00:00 2001 From: Tianchu Chen Date: Fri, 28 Nov 2025 15:53:23 +0800 Subject: [PATCH] char: applicom: fix NULL pointer dereference in ac_ioctl Discovered by Atuin - Automated Vulnerability Discovery Engine. In ac_ioctl, the validation of IndexCard and the check for a valid RamIO pointer are skipped when cmd is 6. However, the function unconditionally executes readb(apbs[IndexCard].RamIO + VERS) at the end. If cmd is 6, IndexCard may reference a board that does not exist (where RamIO is NULL), leading to a NULL pointer dereference. Fix this by skipping the readb access when cmd is 6, as this command is a global information query and does not target a specific board context. Signed-off-by: Tianchu Chen Acked-by: Arnd Bergmann Cc: stable Link: https://patch.msgid.link/20251128155323.a786fde92ebb926cbe96fcb1@linux.dev Signed-off-by: Greg Kroah-Hartman --- drivers/char/applicom.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/char/applicom.c b/drivers/char/applicom.c index 9fed9706d9cd2..c138c468f3a44 100644 --- a/drivers/char/applicom.c +++ b/drivers/char/applicom.c @@ -835,7 +835,10 @@ static long ac_ioctl(struct file *file, unsigned int cmd, unsigned long arg) ret = -ENOTTY; break; } - Dummy = readb(apbs[IndexCard].RamIO + VERS); + + if (cmd != 6) + Dummy = readb(apbs[IndexCard].RamIO + VERS); + kfree(adgl); mutex_unlock(&ac_mutex); return ret; -- 2.47.3