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Re: [PATCH v2] tools/9pfsd: Fix build error caused by strerror_r()
- To: Juergen Gross <jgross@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <xin.wang2@xxxxxxx>
- Date: Thu, 7 Mar 2024 20:26:17 +0800
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- Cc: Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- Delivery-date: Thu, 07 Mar 2024 12:26:30 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Juergen,
On 3/7/2024 7:24 PM, Juergen Gross wrote:
On 07.03.24 11:38, Henry Wang wrote:
Below error can be seen when doing Yocto build of the toolstack:
| io.c: In function 'p9_error':
| io.c:684:5: error: ignoring return value of 'strerror_r' declared
with attribute 'warn_unused_result' [-Werror=unused-result]
| 684 | strerror_r(err, ring->buffer, ring->ring_size);
| | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| cc1: all warnings being treated as errors
Fix the build by using strerror() to replace strerror_r(). Since
strerror() is thread-unsafe, use a separate local mutex to protect
the action. The steps would then become: Acquire the mutex first,
invoke strerror(), copy the string from strerror() to the designated
buffer and then drop the mutex.
Signed-off-by: Henry Wang <xin.wang2@xxxxxxx>
---
tools/9pfsd/io.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/tools/9pfsd/io.c b/tools/9pfsd/io.c
index adb887c7d9..2b80c9528d 100644
--- a/tools/9pfsd/io.c
+++ b/tools/9pfsd/io.c
@@ -680,8 +680,18 @@ static bool name_ok(const char *str)
static void p9_error(struct ring *ring, uint16_t tag, uint32_t err)
{
unsigned int erroff;
+ static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+ char *strerror_str;
+ RING_IDX strerror_len = 0, copy_len = 0;
+
+ pthread_mutex_lock(&mutex);
+ strerror_str = strerror(err);
+ strerror_len = strlen(strerror_str) + 1;
+ copy_len = min(strerror_len, ring->ring_size);
Hmm, I think we even _need_ to cap the string earlier.
A string in the 9pfs protocol is a 2 byte length field plus the string.
In case of a ring larger than 65535 bytes this would mean the result of
strerror() could (in theory) overflow the string format of 9pfs.
Additionally the string should be a _short_ description of the error, so
I'd like to suggest to not use ring_size as the upper bound for the
string
length, but a fixed value defined as a macro, e.g.:
#define MAX_ERRSTR_LEN 80
I can use a macro-defined value in v3, sure.
Kind regards,
Henry
Juergen
|
