linux-kernel - [GIT pull] core/entry for v6.9-rc1

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Date: Sat, 23 Mar 2024 20:51:59 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [GIT pull] core/entry for v6.9-rc1

Linus,

please pull the latest core/entry branch from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-entry-2024-03-23

up to:  fb13b11d5387: entry: Respect changes to system call number by trace_sys_enter()

A single fix for the generic entry code:

  THe trace_sys_enter() tracepoint can modify the syscall number via
  kprobes or BPF in pt_regs, but that requires that the syscall number is
  re-evaluted from pt_regs after the tracepoint.

  A seccomp fix in that area removed the re-evaluation so the change does
  not take effect as the code just uses the locally cached number.

  Restore the original behaviour by re-evaluating the syscall number after
  the tracepoint.


Thanks,

	tglx

------------------>
André Rösti (1):
      entry: Respect changes to system call number by trace_sys_enter()


 kernel/entry/common.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 88cb3c88aaa5..90843cc38588 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -57,8 +57,14 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall,
 	/* Either of the above might have changed the syscall number */
 	syscall = syscall_get_nr(current, regs);
 
-	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
+	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) {
 		trace_sys_enter(regs, syscall);
+		/*
+		 * Probes or BPF hooks in the tracepoint may have changed the
+		 * system call number as well.
+		 */
+		syscall = syscall_get_nr(current, regs);
+	}
 
 	syscall_enter_audit(regs, syscall);