Re: Invalid read of size 1

Derrick McKee <[email protected]>
Newsgroups gmane.comp.debugging.valgrind
Message-ID <CAJoBWHzQ-_+YhHMFBVRQwPqJdUzBDpz9A+mV8wnW1nEixZ9uEw@mail.gmail.com> 
It looks like you're using a pointer that has been freed some time earlier.

On Sun, Jun 7, 2020, 10:52 James Read <[email protected]> wrote:

> I'm getting a series of Invalid read of size 1 errors. These seem to be
> related to strlen() calls. How is it possible for strlen() to make an
> invalid read?
>
> Here is my valgrind output:
>
> ==21737== Invalid read of size 1
> ==21737==    at 0x483EF46: strlen (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10D7E6: crawler_init (crawler.c:1165)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c0 is 0 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x483EF54: strlen (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10D7E6: crawler_init (crawler.c:1165)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c1 is 1 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x483EF46: strlen (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10D89B: crawler_init (crawler.c:1166)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c0 is 0 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x483EF54: strlen (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10D89B: crawler_init (crawler.c:1166)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c1 is 1 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x4993BFD: ??? (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49D0D82: ??? (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759AF: mysql_real_escape_string_quote (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759DB: mysql_real_escape_string (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x10D8BB: crawler_init (crawler.c:1166)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c0 is 0 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x499D751: ??? (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49D0D98: ??? (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759AF: mysql_real_escape_string_quote (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759DB: mysql_real_escape_string (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x10D8BB: crawler_init (crawler.c:1166)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c0 is 0 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
> ==21737== Invalid read of size 1
> ==21737==    at 0x49D0DCB: ??? (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759AF: mysql_real_escape_string_quote (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x49759DB: mysql_real_escape_string (in
> /usr/lib/x86_64-linux-gnu/libmysqlclient.so.21.1.20)
> ==21737==    by 0x10D8BB: crawler_init (crawler.c:1166)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Address 0x7adf2c0 is 0 bytes inside a block of size 52 free'd
> ==21737==    at 0x483CA3F: free (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x10CC43: new_head_conn (crawler.c:911)
> ==21737==    by 0x10D751: crawler_init (crawler.c:1148)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==  Block was alloc'd at
> ==21737==    at 0x483B7F3: malloc (in
> /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==21737==    by 0x50DD50E: strdup (strdup.c:42)
> ==21737==    by 0x10D70C: crawler_init (crawler.c:1145)
> ==21737==    by 0x10E417: main (crawler.c:1383)
> ==21737==
>
> Source code for my app is available at
> https://github.com/JamesRead5737/webcrawler
>
> Thanks,
> James Read
> _______________________________________________
> Valgrind-users mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/valgrind-users
>

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