PR #21151 opened by ruikai URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21151 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21151.patch
Prevents stack overflow with deeply nested repeat/if/proc blocks. Originally reported via ffmpeg-security; this patch incorporates feedback from Kacper Michajlow. >From 1178b51f2ae88ddd4045561b98f4030eb08a531a Mon Sep 17 00:00:00 2001 From: Ruikai Peng <[email protected]> Date: Wed, 10 Dec 2025 01:41:14 +0000 Subject: [PATCH] avfilter/drawvg: limit recursion depth in VGS parser Prevents stack overflow with deeply nested repeat/if/proc blocks. --- libavfilter/vf_drawvg.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) diff --git a/libavfilter/vf_drawvg.c b/libavfilter/vf_drawvg.c index 5d3008084c..97e5583366 100644 --- a/libavfilter/vf_drawvg.c +++ b/libavfilter/vf_drawvg.c @@ -242,6 +242,8 @@ struct VGSParameter { // for the arguments. #define MAX_PROC_ARGS (MAX_COMMAND_PARAMS - 2) +#define VGS_MAX_RECURSION_DEPTH 1024 + // Definition of each command. struct VGSCommandSpec { @@ -435,6 +437,7 @@ struct VGSParser { const char **proc_names; int proc_names_count; + int depth; ///< Current recursion depth while parsing subprograms. // Store the variable names for the default ones (from `vgs_default_vars`) // and the variables created with `setvar`. @@ -1232,6 +1235,7 @@ static void vgs_parser_init(struct VGSParser *parser, const char *source) { parser->proc_names = NULL; parser->proc_names_count = 0; + parser->depth = 0; memset(parser->var_names, 0, sizeof(parser->var_names)); for (int i = 0; i < VAR_U0; i++) @@ -1264,11 +1268,20 @@ static int vgs_parse( int subprogram ) { struct VGSParserToken token; + int ret = 0; memset(program, 0, sizeof(*program)); + parser->depth++; + if (parser->depth > VGS_MAX_RECURSION_DEPTH) { + av_log(log_ctx, AV_LOG_ERROR, + "Exceeded maximum drawvg block nesting depth (%d)\n", + VGS_MAX_RECURSION_DEPTH); + ret = AVERROR(EINVAL); + goto out; + } + for (;;) { - int ret; const struct VGSCommandSpec *cmd; ret = vgs_parser_next_token(log_ctx, parser, &token, 1); @@ -1286,7 +1299,7 @@ static int vgs_parse( FFSWAP(int, program->proc_names_count, parser->proc_names_count); } - return 0; + goto out; case TOKEN_WORD: // The token must be a valid command. @@ -1304,21 +1317,26 @@ static int vgs_parse( if (!subprogram) goto invalid_token; - return 0; + goto out; default: goto invalid_token; } } - return AVERROR_BUG; /* unreachable */ + ret = AVERROR_BUG; /* unreachable */ + goto out; invalid_token: vgs_log_invalid_token(log_ctx, parser, &token, "Expected command."); fail: vgs_free(program); - return AVERROR(EINVAL); + ret = AVERROR(EINVAL); + +out: + parser->depth--; + return ret; } /* -- 2.49.1 _______________________________________________ ffmpeg-devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
