[FIX] Fix segfault in add_cc_sub_text and initialize to NULL in init_encoder #950
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src/lib_ccx/ccx_encoders_common.c
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| @@ -924,7 +924,8 @@ void dinit_encoder(struct encoder_ctx **arg, LLONG current_fts) | |||
| write_subtitle_file_footer(ctx, ctx->out + i); | |||
| } | |||
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| free_encoder_context(ctx->prev); | |||
| if(!ccx_options.hardsubx) // Don't free ctx->prev in case of hardsubx to avoid segfault | |||
| free_encoder_context(ctx->prev); | |||
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Why is that call to free_encoder_context segfaulting? That's what we should fix, not just not do the call because it segfaults... is it because ctx->prev is null, because it ends in a double-free, or what?
This seems like hiding the problem, not fixing it.
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@cfsmp3 Yes, you are right. I didn't go deep enough to investigate the cause of the segfault before your comment.
So the prev field of an encoder_ctx is used to process dvb subtitles. They are not at all used in the code that involves processing hard subtitles. And when an encoder_ctx is initialized in init_encoder function, the prev field is not set to NULL and hence, it gets some random value(address). So, ctx->prev != NULL and free_encoder_context tries to free the fields of ctx->prev, which do not exist, and hence a segfault. So this fix is wrong and the actual fix is very simple. Please check my latest fix.
This commit adds some checks to avoid segmentation faults. * In `add_cc_sub_text()`, strdup will cause a segfault if we duplicate an empty string. * In `init_encoder()`, initialize pointer fields to NULL to avoid random addressing so we can avoid illegal memory accessing and segfaults in other places.
saurabhshah0410
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This commit adds some checks to avoid segmentation faults.
In
add_cc_sub_text(), strdup will cause a segfault if we duplicate anempty string.
In
init_encoder(), initialize pointer fields to NULL to avoid randomaddressing so we can avoid illegal memory accessing and segfaults in
other places.