[FFmpeg-devel] [PATCH 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[FFmpeg-devel] [PATCH 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Cai Fan]

Signed-off-by: Cai Fan <caifan0425@163.com>
---
 libavformat/img2enc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
index 41638d92b8..a1eb0c688d 100644
--- a/libavformat/img2enc.c
+++ b/libavformat/img2enc.c
@@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
     }
     for (i = 0; i < 4; i++) {
         av_dict_copy(&options, img->protocol_opts, 0);
-        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
+        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
+        if (len < 0 || len >= sizeof(img->tmp[i])) {
+            av_log(s, AV_LOG_ERROR, "Filename too long: %s\n", filename);
+            ret = AVERROR(EINVAL);
+            goto fail;
+        }
         av_strlcpy(img->target[i], filename, sizeof(img->target[i]));
         if (s->io_open(s, &pb[i], img->use_rename ? img->tmp[i] : filename, AVIO_FLAG_WRITE, &options) < 0) {
             av_log(s, AV_LOG_ERROR, "Could not open file : %s\n", img->use_rename ? img->tmp[i] : filename);
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Zhao Zhili]

> On Jul 31, 2025, at 10:13, Cai Fan <caifan0425@163.com> wrote:
> 
> Signed-off-by: Cai Fan <caifan0425@163.com>
> ---
> libavformat/img2enc.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
> index 41638d92b8..a1eb0c688d 100644
> --- a/libavformat/img2enc.c
> +++ b/libavformat/img2enc.c
> @@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>     }
>     for (i = 0; i < 4; i++) {
>         av_dict_copy(&options, img->protocol_opts, 0);
> -        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
> +        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
> +        if (len < 0 || len >= sizeof(img->tmp[i])) {
> +            av_log(s, AV_LOG_ERROR, "Filename too long: %s\n", filename);

“filename exceeds buffer size %zu\n”.

> +            ret = AVERROR(EINVAL);
> +            goto fail;
> +        }
>         av_strlcpy(img->target[i], filename, sizeof(img->target[i]));
>         if (s->io_open(s, &pb[i], img->use_rename ? img->tmp[i] : filename, AVIO_FLAG_WRITE, &options) < 0) {
>             av_log(s, AV_LOG_ERROR, "Could not open file : %s\n", img->use_rename ? img->tmp[i] : filename);
> -- 
> 2.34.1
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
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> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

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[FFmpeg-devel] [PATCH v2 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Cai Fan]

Signed-off-by: Cai Fan <caifan0425@163.com>
---
 libavformat/img2enc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
index 41638d92b8..9a5718a8da 100644
--- a/libavformat/img2enc.c
+++ b/libavformat/img2enc.c
@@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
     }
     for (i = 0; i < 4; i++) {
         av_dict_copy(&options, img->protocol_opts, 0);
-        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
+        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
+        if (len < 0 || len >= sizeof(img->tmp[i])) {
+            av_log(s, AV_LOG_ERROR, "filename '%s' exceeds buffer size %zu\n", filename, sizeof(img->tmp[i]));
+            ret = AVERROR(EINVAL);
+            goto fail;
+        }
         av_strlcpy(img->target[i], filename, sizeof(img->target[i]));
         if (s->io_open(s, &pb[i], img->use_rename ? img->tmp[i] : filename, AVIO_FLAG_WRITE, &options) < 0) {
             av_log(s, AV_LOG_ERROR, "Could not open file : %s\n", img->use_rename ? img->tmp[i] : filename);
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH v2 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 1223 bytes --]

On Thu, Jul 31, 2025 at 04:21:35PM +0800, Cai Fan wrote:
> Signed-off-by: Cai Fan <caifan0425@163.com>
> ---
>  libavformat/img2enc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
> index 41638d92b8..9a5718a8da 100644
> --- a/libavformat/img2enc.c
> +++ b/libavformat/img2enc.c
> @@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>      }
>      for (i = 0; i < 4; i++) {
>          av_dict_copy(&options, img->protocol_opts, 0);
> -        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
> +        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
> +        if (len < 0 || len >= sizeof(img->tmp[i])) {
> +            av_log(s, AV_LOG_ERROR, "filename '%s' exceeds buffer size %zu\n", filename, sizeof(img->tmp[i]));
> +            ret = AVERROR(EINVAL);
> +            goto fail;
> +        }

is there a reason this doesnt use av_asprintf() ?
that is allocate as needed

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

[-- Attachment #2: Type: text/plain, Size: 251 bytes --]

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Re: [FFmpeg-devel] [PATCH v2 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Cai Fan]

Hi,

Thank you for the suggestion.

The tmp field in VideoMuxData is a fixed-size embedded array (char tmp[4][1024]), not a pointer. This makes using av_asprintf() not suitable.




typedef struct VideoMuxData {

    const AVClass *class;  /**< Class for private options. */

    int start_img_number;

    int img_number;

    int split_planes;       

    char tmp[4][1024];     // Fixed-size buffer within the struct

    char target[4][1024];

    int update;

    int use_strftime;

    int frame_pts;

    const char *muxer;

    int use_rename;

    AVDictionary *protocol_opts;

} VideoMuxData;

VideoMuxData *img = s->priv_data;





At 2025-08-04 06:57:00, "Michael Niedermayer" <michael@niedermayer.cc> wrote:
>On Thu, Jul 31, 2025 at 04:21:35PM +0800, Cai Fan wrote:
>> Signed-off-by: Cai Fan <caifan0425@163.com>
>> ---
>>  libavformat/img2enc.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>> 
>> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
>> index 41638d92b8..9a5718a8da 100644
>> --- a/libavformat/img2enc.c
>> +++ b/libavformat/img2enc.c
>> @@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>>      }
>>      for (i = 0; i < 4; i++) {
>>          av_dict_copy(&options, img->protocol_opts, 0);
>> -        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        if (len < 0 || len >= sizeof(img->tmp[i])) {
>> +            av_log(s, AV_LOG_ERROR, "filename '%s' exceeds buffer size %zu\n", filename, sizeof(img->tmp[i]));
>> +            ret = AVERROR(EINVAL);
>> +            goto fail;
>> +        }
>
>is there a reason this doesnt use av_asprintf() ?
>that is allocate as needed
>
>thx
>
>[...]
>-- 
>Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
>No great genius has ever existed without some touch of madness. -- Aristotle
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Re: [FFmpeg-devel] [PATCH v2 1/1] libavformat/img2enc.c: rm warning ‘.tmp’ directive output may be truncated

[Marton Balint]

On Mon, 4 Aug 2025, Michael Niedermayer wrote:

> On Thu, Jul 31, 2025 at 04:21:35PM +0800, Cai Fan wrote:
>> Signed-off-by: Cai Fan <caifan0425@163.com>
>> ---
>>  libavformat/img2enc.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavformat/img2enc.c b/libavformat/img2enc.c
>> index 41638d92b8..9a5718a8da 100644
>> --- a/libavformat/img2enc.c
>> +++ b/libavformat/img2enc.c
>> @@ -180,7 +180,12 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
>>      }
>>      for (i = 0; i < 4; i++) {
>>          av_dict_copy(&options, img->protocol_opts, 0);
>> -        snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        int len = snprintf(img->tmp[i], sizeof(img->tmp[i]), "%s.tmp", filename);
>> +        if (len < 0 || len >= sizeof(img->tmp[i])) {
>> +            av_log(s, AV_LOG_ERROR, "filename '%s' exceeds buffer size %zu\n", filename, sizeof(img->tmp[i]));
>> +            ret = AVERROR(EINVAL);
>> +            goto fail;
>> +        }
>
> is there a reason this doesnt use av_asprintf() ?
> that is allocate as needed

Actually I did that extra step and more:

https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20077

So I guess this patch is now obsolete, sorry about that, but it was a 
relatively low hanging fruit.

Regards,
Marton
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