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commit ddc650e9b3dc916eab417ce9f79e67337b05035c
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Author: Andreas Schwab <schwab@suse.de>
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Date: Wed Feb 19 17:21:46 2020 +0100
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Fix use-after-free in glob when expanding ~user (bug 25414)
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The value of `end_name' points into the value of `dirname', thus don't
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deallocate the latter before the last use of the former.
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diff --git a/posix/glob.c b/posix/glob.c
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index cba9cd1819..4580cefb9f 100644
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--- a/posix/glob.c
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+++ b/posix/glob.c
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@@ -827,31 +827,32 @@ __glob (const char *pattern, int flags, int (*errfunc) (const char *, int),
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{
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size_t home_len = strlen (p->pw_dir);
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size_t rest_len = end_name == NULL ? 0 : strlen (end_name);
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- char *d;
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+ char *d, *newp;
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+ bool use_alloca = glob_use_alloca (alloca_used,
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+ home_len + rest_len + 1);
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- if (__glibc_unlikely (malloc_dirname))
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- free (dirname);
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- malloc_dirname = 0;
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-
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- if (glob_use_alloca (alloca_used, home_len + rest_len + 1))
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- dirname = alloca_account (home_len + rest_len + 1,
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- alloca_used);
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+ if (use_alloca)
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+ newp = alloca_account (home_len + rest_len + 1, alloca_used);
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else
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{
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- dirname = malloc (home_len + rest_len + 1);
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- if (dirname == NULL)
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+ newp = malloc (home_len + rest_len + 1);
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+ if (newp == NULL)
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{
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scratch_buffer_free (&pwtmpbuf);
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retval = GLOB_NOSPACE;
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goto out;
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}
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- malloc_dirname = 1;
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}
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- d = mempcpy (dirname, p->pw_dir, home_len);
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+ d = mempcpy (newp, p->pw_dir, home_len);
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if (end_name != NULL)
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d = mempcpy (d, end_name, rest_len);
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*d = '\0';
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+ if (__glibc_unlikely (malloc_dirname))
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+ free (dirname);
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+ dirname = newp;
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+ malloc_dirname = !use_alloca;
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+
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dirlen = home_len + rest_len;
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dirname_modified = 1;
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}
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