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fs: fat: avoid NULL dereference when root dir is full

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When trying to create a file in the full root directory of a FAT32
filesystem a NULL dereference can be observed.

When the root directory of a FAT16 filesystem is full fill_dir_slot() must
return -1 to signal that a new directory entry could not be allocated.

Fixes: cd2d727fff7e ("fs: fat: allocate a new cluster for root directory of fat32")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
This commit is contained in:
Heinrich Schuchardt 2020-11-19 12:24:44 +01:00
parent 7889951d0f
commit 661d223868
1 changed files with 2 additions and 3 deletions
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fs/fat/fat_write.c
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@ -260,9 +260,8 @@ fill_dir_slot(fat_itr *itr, const char *l_name)
flush_dir(itr); flush_dir(itr);
/* allocate a cluster for more entries */ /* allocate a cluster for more entries */
if (!fat_itr_next(itr)) if (!fat_itr_next(itr) && !itr->dent)
if (!itr->dent && if ((itr->is_root && itr->fsdata->fatsize != 32) ||
(!itr->is_root || itr->fsdata->fatsize == 32) &&
new_dir_table(itr)) new_dir_table(itr))
return -1; return -1;
} }