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Probes fixes for v7.3-rc4:

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- kprobes: Fix permanent hang when flushing the kprobe optimizer
   Fix a deadlock when disabling kprobe optimization via sysctl or debugfs
   where flushers hung waiting for optimizer_completion. Replaced the
   completion with an optimizer_passes counter and wait_var_event_mutex()
   under kprobe_mutex so concurrent flushers can wait and wake up safely.
 
 - fprobe: Terminate the fgraph_data list when the reservation is not filled
   Fix an issue where unused shadow stack data left uninitialized by
   fprobe_fgraph_entry() was misparsed as stale fprobe headers on return.
   Explicitly write a zero word to terminate the list and update
   read_fprobe_header() to handle the zeroed slot properly.
 
 - ftracetest: Fix unique symbol check in kprobe_non_uniq_symbol.tc
   Fix false test failures in kprobe_non_uniq_symbol.tc on architectures
   like s390 where a symbol exists once in core kernel but also in modules.
   Anchor the /proc/kallsyms search regex to the end of the line so that
   module symbols are not incorrectly counted.
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Merge tag 'probes-fixes-v7.3-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull probe fixes from Masami Hiramatsu:

 - kprobes: Fix permanent hang when flushing the kprobe optimizer

   Fix a deadlock when disabling kprobe optimization via sysctl or
   debugfs where flushers hung waiting for optimizer_completion.
   Replaced the completion with an optimizer_passes counter and
   wait_var_event_mutex() under kprobe_mutex so concurrent flushers can
   wait and wake up safely.

 - fprobe: Terminate the fgraph_data list when the reservation is not
   filled

   Fix an issue where unused shadow stack data left uninitialized by
   fprobe_fgraph_entry() was misparsed as stale fprobe headers on
   return. Explicitly write a zero word to terminate the list and update
   read_fprobe_header() to handle the zeroed slot properly.

 - ftracetest: Fix unique symbol check in kprobe_non_uniq_symbol.tc

   Fix false test failures in kprobe_non_uniq_symbol.tc on architectures
   like s390 where a symbol exists once in core kernel but also in
   modules. Anchor the /proc/kallsyms search regex to the end of the
   line so that module symbols are not incorrectly counted.

* tag 'probes-fixes-v7.3-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  kprobes: Fix permanent hang when flushing the kprobe optimizer
  fprobe: Terminate the fgraph_data list when the reservation is not filled
  selftests/ftrace: Fix unique symbol check in kprobe_non_uniq_symbol.tc
This commit is contained in:
Linus Torvalds 2026-09-26 08:36:29 -07:00
commit efb27d4767
3 changed files with 30 additions and 9 deletions
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22
kernel/kprobes.c
View File

@ -42,6 +42,7 @@
#include <linux/execmem.h>
#include <linux/cleanup.h>
#include <linux/wait.h>
#include <linux/wait_bit.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>
@ -526,7 +527,8 @@ enum {
OPTIMIZER_ST_FLUSHING = 2,
};
static DECLARE_COMPLETION(optimizer_completion);
/* Bumped at the end of each kprobe_optimizer() pass, under 'kprobe_mutex' */
static unsigned long optimizer_passes;
#define OPTIMIZE_DELAY 5
@ -654,9 +656,9 @@ static void kprobe_optimizer(void)
do_free_cleaned_kprobes();
}
/* Step 5: Kick optimizer again if needed. But if there is a flush requested, */
if (completion_done(&optimizer_completion))
complete(&optimizer_completion);
/* Step 5: Wake up flushers, and kick optimizer again if needed. */
optimizer_passes++;
wake_up_var_locked(&optimizer_passes, &kprobe_mutex);
if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
kick_kprobe_optimizer(); /*normal kick*/
@ -708,7 +710,8 @@ static void wait_for_kprobe_optimizer_locked(void)
lockdep_assert_held(&kprobe_mutex);
while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
init_completion(&optimizer_completion);
unsigned long passes = optimizer_passes;
/*
* Set state to OPTIMIZER_ST_FLUSHING and wake up the thread if it's
* idle. If it's already kicked, it will see the state change.
@ -717,9 +720,12 @@ static void wait_for_kprobe_optimizer_locked(void)
OPTIMIZER_ST_FLUSHING) != OPTIMIZER_ST_FLUSHING)
wake_up(&kprobe_optimizer_wait);
mutex_unlock(&kprobe_mutex);
wait_for_completion(&optimizer_completion);
mutex_lock(&kprobe_mutex);
/*
* kprobe_optimizer() holds 'kprobe_mutex' for a whole pass, which
* this drops while sleeping, so a new count means a full pass ran.
*/
wait_var_event_mutex(&optimizer_passes,
optimizer_passes != passes, &kprobe_mutex);
}
}

15
kernel/trace/fprobe.c
View File

@ -171,6 +171,11 @@ static inline bool write_fprobe_header(unsigned long *stack,
static inline void read_fprobe_header(unsigned long *stack,
struct fprobe **fp, unsigned int *size_words)
{
if (!*stack) {
*fp = NULL;
*size_words = 0;
return;
}
*fp = arch_decode_fprobe_header_fp(*stack);
*size_words = arch_decode_fprobe_header_size(*stack);
}
@ -203,6 +208,12 @@ static inline void read_fprobe_header(unsigned long *stack,
{
struct __fprobe_header *fph = (struct __fprobe_header *)stack;
if (!*stack) {
*fp = NULL;
*size_words = 0;
return;
}
*fp = fph->fp;
*size_words = fph->size_words;
}
@ -635,6 +646,10 @@ static int fprobe_fgraph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops
}
}
/* Terminate the list, fgraph_reserve_data() does not clear it. */
if (used && used < reserved_words)
fgraph_data[used] = 0;
/* If any exit_handler is set, data must be used. */
return used != 0;
}

2
tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
View File

@ -6,7 +6,7 @@
SYMBOL='name_show'
# We skip this test on kernel where SYMBOL is unique or does not exist.
if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}" /proc/kallsyms)" -le '1' ]; then
if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}$" /proc/kallsyms)" -le '1' ]; then
exit_unsupported
fi