From: Thorsten Blum <thorsten.blum@linux•dev>
To: Madhavan Srinivasan <maddy@linux•ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>,
Nicholas Piggin <npiggin@gmail•com>,
"Christophe Leroy (CS GROUP)" <chleroy@kernel•org>,
Srikar Dronamraju <srikar@linux•ibm.com>,
Shrikanth Hegde <sshegde@linux•ibm.com>
Cc: Thorsten Blum <thorsten.blum@linux•dev>,
linuxppc-dev@lists•ozlabs.org, linux-kernel@vger•kernel.org
Subject: [PATCH] powerpc: rtas: use get_user to simplify manage_flash_write
Date: Thu, 28 May 2026 22:12:27 +0200 [thread overview]
Message-ID: <20260528201226.1599977-3-thorsten.blum@linux.dev> (raw)
Drop the local 10-byte buffer. The old code copied at most 9 bytes from
the user buffer, but only the first byte was used to select the RTAS
operation.
Use get_user() to read the command byte instead and compare it directly
with '0' and '1'. Drop the explicit user buffer check, since get_user()
will fail on a NULL pointer and correctly return -EFAULT instead of
-EINVAL. Remove the now-obsolete string constants as well as any
strncmp() and strlen() calls.
Return the original count instead of a potentially capped value, since
the full user write has been consumed once the command is accepted.
Use unsigned int op to better match the manage_flash() interface.
Signed-off-by: Thorsten Blum <thorsten.blum@linux•dev>
---
arch/powerpc/kernel/rtas_flash.c | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index 583dc16e9d3c..722dbfb6fbf8 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/arch/powerpc/kernel/rtas_flash.c
@@ -394,30 +394,23 @@ static ssize_t manage_flash_write(struct file *file, const char __user *buf,
size_t count, loff_t *off)
{
struct rtas_manage_flash_t *const args_buf = &rtas_manage_flash_data;
- static const char reject_str[] = "0";
- static const char commit_str[] = "1";
- char stkbuf[10];
- int op;
+ unsigned int op;
+ char cmd;
guard(mutex)(&rtas_manage_flash_mutex);
if ((args_buf->status == MANAGE_AUTH) || (count == 0))
return count;
- op = -1;
- if (buf) {
- if (count > 9) count = 9;
- if (copy_from_user (stkbuf, buf, count))
- return -EFAULT;
- if (strncmp(stkbuf, reject_str, strlen(reject_str)) == 0)
- op = RTAS_REJECT_TMP_IMG;
- else if (strncmp(stkbuf, commit_str, strlen(commit_str)) == 0)
- op = RTAS_COMMIT_TMP_IMG;
- }
-
- if (op == -1) { /* buf is empty, or contains invalid string */
+ if (get_user(cmd, buf))
+ return -EFAULT;
+
+ if (cmd == '0')
+ op = RTAS_REJECT_TMP_IMG;
+ else if (cmd == '1')
+ op = RTAS_COMMIT_TMP_IMG;
+ else
return -EINVAL;
- }
manage_flash(args_buf, op);
return count;
reply other threads:[~2026-05-28 20:13 UTC|newest]
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