[patch] HWBKPT FIX: Release the bp slot ifarch_validate_hwbkpt_settings() fails.

[Mahesh Salgaonkar]

On a given architecture, when hardware breakpoint registration fails due
to un-supported access type (read/write/execute), we loose the bp slot since
register_perf_hw_breakpoint() does not release the bp slot on failure.
Hence, any subsequent hardware breakpoint registration starts failing
with 'no space left on device' error.

This patch introduces error handling in register_perf_hw_breakpoint()
function and releases bp slot on error.

Signed-off-by: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
---

 kernel/hw_breakpoint.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)


diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 50dbd59..c030ae6 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -296,6 +296,10 @@ int register_perf_hw_breakpoint(struct perf_event *bp)
 	if (!bp->attr.disabled || !bp->overflow_handler)
 		ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
 
+	/* if arch_validate_hwbkpt_settings() fails then release bp slot */
+	if (ret)
+		release_bp_slot(bp);
+
 	return ret;
 }
 

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